Urban Drainage Mapping

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[Why Urban Drain Mapping?]

Urban drainage consists of drains, ditches, culverts, tunnels, and other features that move water across the landscape. Drains and water flows can be complex in urban areas. Low-income settings with stressed infrastructure budgets may be unplanned or built on an ad-hoc basis. If maintenance or construction is less than optimal, the efficiency of moving water can be compromised, in the worst situations leading to life threatening flooding.

Evaluation of the existing drain network can lead to well informed recommendations so the most cost effective or needed repairs, maintenance or improvements can be done first. In situations where construction blueprints are lost, inaccessible or unreliable, surveying needs to be undertaken to record the actual location and size of drains. This data can then be entered into a computerized hydrological model.

[Hi Tech meets Low Tech]

Modern computer hydrological modelling can provide potentially life saving information but requires detailed data and sophisticated education to operate accurately. Open data technology combines technology commonly available (Android phones) with the simple idea of getting small local answers to questions. Surveys ask small questions that can be straightforward and easy to measure or answer. When the answers are combined together, they can form a powerful dataset that can answer big questions. Simple tools, and relatively quick training can equip local people with the ability to be contributors to these kinds of data sets.

In low-income settings, community members can be recruited to work very cost efficiently compared to professional survey companies. The opportunity to combine paid employment with training and skill development is attractive and also contributes to the development of social capital.

At the same time, remember that the complex interaction of technical knowledge, training, data verification, and field situations that can change radically within the same urban area means that both management needs and technical skill needs must be evaluated realistically. Some high-level skill sets are needed by projects as well.

[The Open Data Community Participation Model]

The Open Data Kit for Android phones has proved a robust software technology. As an App installed on an Android, it is versatile enough to gather text, numbers, GPS coordinates and even photographs. Customized surveys can be set up in XLSForm, a specialized version of the widely familiar Excel software. These surveys can then be downloaded onto Android phones. The answers are then uploaded to a server. In turn, the data can be used to make a layer of that information that can be put transparently over a map. In turn, this provides for the possibility of powerful visual presentation of information and issues.

Some projects provide community residents with Android phones to gather datum, others require that participants have their own phones. The use of phones already existing in the community can be compensated by a small daily reimbursement.

[A Descriptive Example from Tanzania]

Ramani Huria 2 is a project in Dar es Salaam, Tanzania, which began in August 2017 and scheduled to last 24 months. It follows an earlier project (Ramani Huria 1) done in 2015 that also located drains, but did not gather sufficient data for hydrological mapping. RH2 has developed new data gathering protocols working with the project hydrological engineers. Deltares applied research institute (Holland) has unique software that can model water flow in systems given dimensions of the water pathways.

Ramania Huria 2 was invited to work with Ardhi University students completing the Industrial Training component of their degree work. The contract was awarded to Humanitarian OpenStreetMap (HOT) because of their unique experience and track record in working with open data gathering, mapping and data modeling projects.

Some expat management and trainers were brought in to work on the project. University graduates (who had experience in the first project) were available as Supervisors, each being responsible for a small group of student crew leaders, who in turn were responsible for about 5 students each in the overall group of 300.

The goal of the project is to accurately gather data and present it to improve flood resilience and save lives. A large group (about 200) was initially tasked with using JOSM (a software for manipulating map components) to outline the structures in Dar (Remote Mapping), a preliminary to data gathering about those buildings to contribute to Open Street Map, putting both infrastructure resources and potential trouble spots “On the Map.”

Another group (about 20 students) travel to various city Wards, recruiting community members to use ODK to interview fellow city residents, gathering their reports of flooding at particular GPS coordinates. This information should update a previous survey effort and reflect changes in residency, and increased rainfall in Dar in the last 2 years.

Simultaneously, training was begun for QGIS (a mapping software) work (again, about 20 students) and experimental Surveys and tools were designed for field data gathering. Some students had previous experience with QGIS, but required additional training and supervision to hone their skills to the level required for the project. The QGIS maps can take data gathered by ODK surveys on phones and show polylines and points. Because the GPS on the phone is not perfectly accurate, lines and points need to be aligned with roads properly.

The Survey group (also about 20 students) practiced with early versions of the surveying rods and forms, and through experience, gained skills in trouble shooting some of the configuration particulars of the ODK and the Android phones. As they practiced, and were encouraged in self-leadership skills, the teams improved accuracy and productivity and provided constructive improvements to tools and methods. Some of the GIS team are tasked with providing printed maps so the teams can stay organized. They create these in composer on QGIS. Composer maps are also made for “Errors and Omissions” assignments to particular locations when something is missing, and not explained by notes.

As mentioned, professional engineers are necessary to analyse the data gathered for hydrological models. Additionally, skilled managers will be needed to do training and provide guidance for the project deliverables. Technical glitches can plague the data transfer in early stages of project development. Despite these challenges, Open Data continues to show its versatility and effectiveness when well managed and curated to deliver information to policy and decision makers.



Providing connected line and point data that unambiguously report all the information about drain systems that can be accurately derived from field visits.

Mapping these features in sufficient detail to be useful for hydrological modelling is a new challenge for OSM.

Modern software has the ability to make complex calculations of water flow over a network, but requires data to be submitted within specified parameters.

In order to do hydrological modelling, these connected drains should end in natural waterways or low elevation sinks. Direction of water flow should be field surveyed since topological information can be unavailable or of insufficient detail in flood plains.

[Overview of Project Needs]


Work should be done safely and with the support of local stakeholders. Sufficient resources should be allocated to ensure the success of the project.

Safety varies by context, but might include elements like field teams working in a minimum of pairs, or issuing safety vests for those working along major roadways. Social or urban conditions may be a consideration in some contexts.

[Data Model]

A drainage mapping project needs a Data Model, preferably one that will adhere to international standards, (for example the ODK wiki model).

Ramani Huria has been using OpenDataKit (ODK) with the GeoTrace feature to record drain polylines, and drain points. Polylines and Points conform to geometric standards in GIS mapping programs, for example QGIS. Polygons are not applied in the process of drain mapping, but are very important to make clear work assignment areas on paper maps. They will probably be useful in the data analysis and presentation phase to show, for example, water shed drainage polygons.

The data model is a key component, and may have to be adjusted for local conditions and specific types of drains, however many elements will be ubiquitous everywhere. Part of the discovery process will be research into the local drains and adjusting the model to local conditions. Conditions will vary by neighbourhood, region, country and culture.

Here is the OpenStreetMap wiki on “features.” This link directs particularly to the subsection on “Man Made Waterways.”


Ramani Huria 2's contribution to defining particular feature attributes for Drains will be developing here (look lower on the page since it also includes details on roads:

Dar es Salaam/Ramani Huria

For a good general introduction to humanitarian mapping using OpenStreetMap go here:


For a series of video tutorials introducing novices to the technology and software of open source mapping:

Video tutorials

[Local Political and Cultural Knowledge]

Local knowledge is important when undertaking a project. Technical conditions can change, for example availability of cellular signal. Environmental conditions change with the change of seasons. Cultural conditions can change between locations in the same country, and there may be different challenges or opportunities between urban and rural situations. The potential of cooperation with government agencies will be particular to the context of each project. In some places, as election time is near, safety needs should be evaluated at appropriate intervals.

[Research of Available Documentation]

An evaluation should be undertaken to determine the availability and potential value of existing documentation. In some cases, the practical concerns of actually accessing this documentation might mean that it is not efficient to track it down. In other cases, interagency communication and communication among stakeholder groups will be worthwhile.


One particular need of research has acquired the slang term "fixing." This refers to accessing local knowledge about prices or availability of any variety of materials, tools or skills. Local knowledge is almost essential in many cases and yet the relationship with individuals offering their knowledge as informers or assistants must be done with the awareness that in low income settings, this knowledge may be considered part of their employability or value. Trust should ideally be built over time between those individuals and the project managers.


Platforms like Open Data Kit and free of charge software like QGIS are readily available, but that does not mean that they are unsophisticated. With time and practice (and probably teaching and coaching) the skills can be learned. However, to successfully create usable data requires a high degree of competence and experience. The need for management and training skills to initiate and manage a project should not be underestimated.


Mapping urban drainage is best done as a group effort. The team approach is ideally suited to the open data community’s strengths. Similar to most open data projects, there are by nature many "moving parts" in a drain mapping project Skills ranging from technical to people management, and occasionally "street smarts," are all valuable, and should be available to the project, either in direct staff or in mentorship or collegial associations.


Objectves involving differing skills and responsibilities are an obvious way to organize activities. The Ramani Huria 2 project has the following Departments:

·     Management

·     Finance

·     Research

·     Survey

·     GIS

·     Computing Analysis

For a drain mapping project to be successful, several different types of activities need to be orchestrated. Each department must have access to appropriate tools, processes, and training or skills.

[Interagency Communication]

The benefits of collaborating with other stakeholders can be beneficial, but can take considerable time and skilled resources. Each project should evaluate potential contacts and assign a value ranging between necessary to “non-essential.”


The management group has several highly skilled task areas, and appropriately skilled personnel are required to fulfil these duties, including the management skills to oversee the project in general.

[Financial Accountability and Legal Status]

A project will potentially involve a budget that is large by local standards because of its scale.

Consideration should be given to the legal structure of the project so that it will meet the project needs. Ideally a project will have appropriate structures in place, for example NGO status.

Accounting system should be of a standard appropriate to international standards, and modified for the particular needs of the project.

[Research, Design, Interagency Communication]

A discovery process should be undertaken using the actual drain system and first editions of survey forms. As any new types of features are discovered, they can be incorporated into subsequent editions of the forms. Using this method of “a bias for action,” or “act instead of plan,” gives immediate feed-forward to the system as it develops.

Local knowledge is a key factor in discovering options and limitations for equipment design and availability. Surveyors themselves will have beneficial suggestions. Nevertheless the design process is a complex one demanding experience, knowledge, and intuition to do well.

Additionally, thought should be given to the needed level of communication between other agencies, government bodies, community groups and any other stakeholders.

[Field Surveying Supervision]

While surveying staff can be encouraged to self-lead and self-manage, the training involved will take some time and attention and coaching to develop. And an ongoing review should be undertaken by skilled managers to confirm that systems are working on an ongoing basis. Also from time to time, systems may need to be adapted as field conditions dictate (different areas of the city, or new types of drains or any other change in conditions.

[GIS department]

The level of GIS skill to manage properly and troubleshoot difficulties is not to be underestimated. While our project in Dar es Salaam worked with students who had previous training in QGIS, they required extra coaching to work with the specific problems of mapping drains and creating paper maps for field surveying.

QGIS is Open Source software suitable for many professional and humanitarian applications.

One example of a free of charge online training program is here:


[Computing Analysis and Hydrological Modelling]

This is a job where professional engineers are needed to analyse data. They will also create presentations that are informed and persuasive for recommending maintenance, repair, or improvement priorities.



Consideration should be given to the amount of time that it should take to get the project going with a solid enough foundation. Factors might be the existence of alliances with other stakeholders or governing agencies, level of local knowledge existing on the team or accessible, requirements for office space where equipment can be safe and secure, conditions for staff employment (local and expat), transportation needs.Some time and attention should be budgeted for making appropriate alliances to support project success.

Informal research should be undertaken to get a good representative sample of drainage component types. They should be named in clear and unambiguous language, and a descriptive and visual glossary should be developed. New elements that are discovered after the initial phase of work can be added at a later date. The existing data model can be used as a beginning template.

This can lead to the development of surveys. Initially three kinds of surveys can be used (1) Surveyor Registration, (2) Polyline survey (3) Point survey.

Examples of ODK forms.

[Data Model]

As mentioned above, a model will best be useful if it is in accord with previously established standards in the ODK data model. However, it will probably need to be adjusted for use in different countries.

In the QGIS mapping software, lines are called Polylines (since mathematically they are a series of connected lines formed by points). QGIS also can handle Points and Polygons. For the requirements of hydrological analysis the basic elements are polylines and points.


Drain (ditch, built drain, material, covered or open) culvert, natural waterway (where it can be safely surveyed)

Another type is “Road with no Drain.” Surveying a line through the use of the GPS trace makes these roads show as being reviewed in the field, rather than being left ambiguously blank.

NOTE: Forms should include a “Comment section” to allow free entry of text by field surveyors.


Points that are part of the drain system can include

·     highest elevation of that branch of the drain system

·     point where drain system enters natural watercourse

·     incorrectly constructed point (missing connection to down flow)

·     culvert beginning, but can not deduce where it goes

·     bridge crossing drain segment

(Points, but ones that are not options on any currently used form version)

·     Location of new feature with description

·     Unusual situation that needs text comment

·     Other innovative use of this option designed by field surveyors

NOTE: Forms should include a “Comment section” to allow free entry of text by field surveyors.

[Surveyor Registration Form]

ODK surveys automatically record the IMEI (International Mobile Equipment Identity—a unique 15 digit code) of a phone that is submitting data to the server (uploading a form), and therefore are useful to the project managers. The data submitted can be correlated to each surveyor using a VLOOKUP formula. This enables contribution and participation, as well as the important issue of troubleshooting any particular phone that is giving inaccurate readings.

This surveyor registration form is the ideal place to test the GPS capabilities of each individual phone and find out if it can actually take a line and point. Some particular phone models have insufficient technical capacity, are damaged, or (occasionally) are Windows phones masquerading as Androids that actually have no ability to work with ODK.

[Designing the Organizational Structure]

A drain mapping project needs various departments to ultimately provide usable accessible accurate data:


As discussed above, management orchestrates the complex interaction of widely varying activities and must manage the finances and legalities associated with a project as well as interaction with other stakeholders or agencies. A team is best assembled prior to deployment in the location, as the management team may easily include a component of expat members.

The management team will probably be the authors of at least the first versions of the ODK surveys used in the discovery process.

[Computing Analysis]

This area demands specialized knowledge including various aspects of data analysis or even revisions to existing tools by programming. For example, Ramani Huria invited a computer programmer to make changes in ODK to improve GIS recording tolerances.

A project needs data in a format which can be analysed and a method of analysing that data in addition to the skills and expertise to display the results in various formats appropriate to individual stakeholders or stakeholder groups. In the Ramani Huria 2 project, a Dutch applied research institute specializing in hydrology (Deltares) is using software to analyse the data provided. With this they will be able to create informative visual explanations of the issues involved as well as technical reports and recommendations.

[Research department]

can be tasked with developing tools, processes and training requiring other kinds of data gathering and information necessary to the project success. An example is community member led interviews to research local knowledge of historical flood events to provide a second sober look at water flow data models, or researching locally available products or services.

[GIS department]

may work with gathered data to produce relevant visual representations that can assist in data review AND create assignment areas for organized data collection that will assist the data gathering by the Survey department to be as complete as possible without duplication or revisiting.

[Survey department]

The survey department itself designs measurement tools, processes, and training specifically adapted to local conditions and resources for gathering the dimensions of drains and a method of recording the results.

[Proportional Suggestions (TABLE)]

The following model is based on a group of 18 field surveyors working in teams of three. For 18 surveyors, these numbers below represent approximations of the needed personnel assignments to support an urban drain survey project.

Department Task Skill Level # Subtotal for Dept
Management Business Professional 1
Data/GPS trainer consultant Professional 1
Team Trainer Professional 1 3
Computing Analysis Hydrological Modelling




Research Dept Miscellaneous Skilled 1
Bookkeeping Skilled 1
Field Purchases Junior Skilled 1 3
GIS Supervisor Skilled 1
Maps for Surveyors Intern 2
Errors Printed Maps Intern 2
Segment Correction Intern 4
Data Analysis QIS Intern 2 11
Field Surveyors Supervisor Skilled 2
Crew Leaders Intern 6
Crew Staff Intern 12 18



A number of elements have to be in place before a survey can actually be done and data actually uploaded to a server where it can be accessed and shown on a map.

·     A server must be ready to accept the data

·     Forms must be made in XLSForm and transferred to an application like KoboToolbox

·     Software must be installed on the phone (including ODK, OSMAND, WhatsApp for example

·     Phones must be configured as needed and registered

·     An area for testing the initial forms and phones must be located (with appropriate consideration to permissions and conditions and needs).

·     Survey tools (including safety equipment) must be available

[Setting up a Server]

Data sites like Kobo Toolbox allow users to store data for projects, however a drain survey project may take considerable storage space. For example, the RH2 forms require a photograph of each feature surveyed for future reference. This requires dedicated capacity, and requires technical know how to set up.

[Making a Form with XLSForm]

Here is an introductory page with a video that briefly explains how XLSForm is part of the Open Data Kit.


The XLSForm is where the actual surveys that will be used are designed and generated. Questions can be made according to many formats—text or number answer, multiple choice, answers that then branch into a separate subset of choices or questions. Possible fields also include GPS points and polylines, photographs, even signatures.

XLSForm provides a good online guidebook to the process here:


[Considerations for Assignment Areas to survey]

The goal of surveying is to provide segments and points (with desired attributes recorded) that are connected in a network.

Working from low elevations (ocean, lake or natural watercourse) to higher elevations in the urban area can most quickly provide the hydrological engineers with information to begin evaluating.

Each area should be considered for the possible [unfinished sentence!]


[ODK (Open Data Kit)]

has proven to be extremely robust (in part because it was developed alongside early versions of Android) for data collection and uploading. Every surveyor should have the same version of ODK installed, and a process should be undertaken to ensure that Settings conform amongst the Surveyors in agreement with project needs and decisions.

Knowledgeable ODK managers should review all settings and decide upon a configuration suited for their circumstances. For example, one project may wish to automatically send forms after completed, but another may wish to have forms reviewed by field supervisors before sending to check on quality.

[ODK Modifications]

Ramani Huria has had the good fortune of receiving bespoke modifications to ODK in response to certain technical challenges involved with mapping drainage, which has small tolerances when attempting to show polylines and points in an unambiguous fashion. These are available for sharing.

Our branch of ODK Collect: https://github.com/zestyping/collect/tree/ping/geotrace

QGIS plugin for converting ODK data: https://github.com/zestyping/odk_csv

Web map for viewing KoboToolbox data: https://github.com/zestyping/koboviewer


has worked well as a message platform to communicate both intra and inter-departmentally and of course can include specific managers. Text and pictures and locations are the usual content, and all are helpful at different moments. One member from each team can be assigned to be the main communications officer in the field.


is flexible, though Google is the most common. Ramani Huria has developed programming which pushes uploaded forms to a web page with an OSM background map to display uploaded points and polylines in real time, which currently works only in a current version of Google Chrome.

This web page, and programming is available for sharing. View at https://kf.turkus.net/map/

Username: ramanihuria  Password:

[OSMAND (OpenStreetMap for ANDroid)]

is the usual open data standard, and requires downloading from OSM (for appropriate area).



Previous experience has shown that phones need to be both registered and tested.

For more detailed information on technical specification

[Registration of the Phone]

Each phone used by the project can achieve surveyor identification and phone GPS testing simultaneously by creating a form that includes name (and any other relevant organizational information) as well as a point and line test.

This can be done through a simple ODK form linking the name of the user uniquely to the IEID of that particular phone, and allows for cross-referencing of user with survey submitted. It should be emphasized repeatedly that anyone bringing a new phone must register that new phone, because there can be a tendency for surveyors to simply replace a non-working phone and not mention it, thinking that they will be helping out by not mentioning it. In fact, the opposite is true, because an unregistered phone will make correlation between surveyor and survey impossible until the user is subsequently identified, causing delay and confusion.

[Testing of the Phone]

The registration form will test the capability of the phone to take GPS information. This is necessary for a couple of reasons:

·     “Windows” phones do not have the technical capacity to run the software required for data gathering. (Some Windows phones are designed to superficially mimic the look and behaviour of Androids).

·     An Android phone refusing to pick up a GPS signal, either through damage or faulty manufacturing.

[Settings Configuration]

Phone configurations and available memory need to be reviewed by the management to make standards appropriate to the project. For example, ODK itself takes approximately 500 Mb, and leaving some substantial room for forms means that users should ensure that they have 1Gb free on their forms.

APPENDIX I has more detail about issues involved in phone configuration, but should be considered as only a guide. Each project needs to understand their own needs and experiment as necessary.

[Protocol Documentation]

It may be helpful to provide written guidelines in a form that can provide information for Surveyors and Team Leaders (as a reference for experienced members, as a guideline for new members).

A protocol document can include any relevant information for field procedures.

An example of a protocol Document is found in the APPENDIX II

[Ongoing Evaluation and Review]

In order to understand the interaction of field activity, actually using the ODK, and the hardware performance, especially during the initial phases of a project. For example, one programming innovation that was very helpful to the project did not work on certain phones. When the Surveyors investigated, they discovered that the new innovation required using a specific browser. Some Surveyors have great knowledge about Android phones, and their assistance should be enlisted.

[Battery Rating]

Different phones have different battery life and can perform or be used differently, affecting battery life. Even highly rated batteries can easily run out of power in a full day’s surveying when several Apps are in ongoing use. One solution is to provide recharging power banks to extend usage time.


[Measuring Tools]

Rods were made out of pre-cut wood approximate 2 x 4 x 250 cm, and marked by the centimetre. A 25cm T was added to the bottom for easy measuring of the bottom of drains without the necessity to climb down inside. Tape measures were purchased (metric) 5m.

250cm rods proved to be extremely unpractical for transportation, and a current modification uses a ~15cm strap hinge (total 30cm when open) and a barrel bolt latch for securing the rod to a full length for actual fieldwork. (It then can fold for ease of transportation to ~125cm in length. A handle can be attached of rope, and another bolt mechanism can secure the two halves in a folded position for transport.


[Printed Maps for Assignments]

Printed Maps require procedures to be developed but can be helpful when well designed and articulated. Mapmakers need clear direction to include helpful elements such as legends, Surveyors need clear assignments in order to be successful.

Ideally maps should contain:

1.  Insets that locate the specific assignment (smaller) within recognizable landmarks in a larger urban area for orientation.

2.  Legends to communicate salient information such as project title, date, draughtsperson name, number in series, neighbourhood area, etc.

3. Scalebar accurately calibrated to map.

4.  Compass Rose

5.  Key to identify map features visually

Lamination of Maps can help in discussion. They can be marked with whiteboard markers, then cleaned if plans are readjusted.

Data Scratch Cards or Packages usually need to be provided for volunteers / students / community members who are operating as Surveyors for a project.

[Clothing and Identification and Sustenance]

Two situations are ubiquitous in drainage mapping, the drain running concurrent (or across) to a motor vehicle roadway, and the transition to natural watercourses.

Safety Vests Due to the proximity of traffic, safety vests are recommended for surveyors. Safety should be taught and practiced.

Comfortable clothes and shoes appropriate to physically active outdoor work. In some cultural environments, women will have to gain special permission to wear trousers if desired, for example. In tropical environments, people may be accustomed to wearing sandals, which may or may not be equal to the task of moving about safely. The issues, if any, can be discussed between Surveyors and project managers.

Rain gear is a consideration in many regions near the equator that are often low income settings at higher risk of flooding due to historical levels of infra structure investment.

Identification Cards can be a great asset, as Surveyors also, de facto, are often the public face of the project. In the majority of cases, public interaction is favourable when people understand the nature of the project. In a few cases, diplomatic skills may be necessary to communicate patiently the nature of the project and the shared benefit to participation, for example when it is needed to go temporarily onto private property to connect a series of drains to its final connection into a natural watercourse.

Food and Water are necessities during the active physical work of surveying,  and arrangements should be made such that the Surveyors have the time and permission to take appropriate refreshment and hydration.


Transportation needs to be considered for anything larger than a very local area reachable by walking. Each project will have to design a balance between transporting in vehicles and walking or public transit. The more time spent in transport will result in less surveying on the ground.

With folding rods, a team of 3 can comfortably fit into a 3 wheeled vehicle. Our current model is for teams to meet in the field, having arrived with public transport, bringing their folding survey rods from home, and then return in the afternoon to our headquarters to receive new mapping instructions for the next day.


Place holder for description of field process and choreography

APPENDIX I Know your Phone

Checking your Phone

For an example of the kind of phone specs that are needed:

These are the specs for TeknoW5 phones that were purchased for the project:

PHONE 1 Tekno W5
2 SIM Cards
1 SD CARD 16 Gb
1 Protective Cover
1 Charger
SPECS Processor 1.3 Giga Hertz QUAD CORE
Camera 13Mega Pixel Front Camera
Hard Drive 16 Giga Byte
Ram 1 Giga Byte
Battery 3000 milli Ampere hours
Android Version 6.0
Kernal Version 3.18.19+
Dual SIM

Understanding Specifications (Specs):

THE PHONE – 2 SIM card slots may be helpful in some locations to switch to the best provider.

Subscriber Identity Module a microprocessor in a mobile phone holding details of the user's network registration, payments, messages, calls, etc. Also (in full SIM card): a card bearing such a microprocessor, which may be transferable between compatible phones.

If you have an SD card, it will give you some room to hold photos.

SD card (Secure Digital card)—4 types—SDSC (standard capacity) SDHC (High-capacity) SDXC (EXtended capacity) and SDIO (Input Output type)

The three sizes available are Original, Mini, and Micro.

Gigabytes (GB)

1 000 000 000 Bytes

7 minutes of HDTV video OR 114 minutes of audio is about one GB. 16 GB can hold about 10 000 photos, or 4 hours of video. Apps, photos, games, and music can use up your phones memory. That is why it is good to have a SD card, and organize your FILE MANAGER so that some things are stored on it. (OSMAND and ODK will still be on the phone memory)

Megapixels File size (MB) 1GB 2GB 4GB 8GB 16GB 32GB 64GB 128GB
4MP 1.2 715 1430 2861 5722 11444 22888 45776 91552
5MP 1.5 572 1144 2288 4577 9155 18310 36620 73240
6MP 1.8 476 953 1907 3814 7629 15258 30516 61032
7MP 2.1 408 817 1634 3269 6539 13078 26156 52312
8MP 2.4 357 715 1430 2861 5722 11444 22888 45776
10MP 3.0 286 572 1144 2288 4577 9155 18310 36620
12MP 3.6 238 476 953 1907 3814 7629 15258 30516
14MP 4.2 204 408 817 1634 3269 6539 13078 26156
16MP 4.8 178 357 715 1430 2861 5722 11444 22888
22MP 6.6 130 260 520 1040 2080 4161 8322 16644


It is hard to get fully waterproof phones in Sierra Leone, or waterproof cases, so a zip lock plastic bag is a good idea, though you will have to treat it gently to extend its life. (The zip lock bag can also be used to hold a notebook)

We often find phones that don’t have enough room for the ODK and OSMAND, and some things need to be erased or uninstalled to make room


Charger – One plug in Charger and one Motorcycle charger – the low price is 15,000 for a motorcycle charger in Kenema from the guy that makes them.

Processor –

This is the “brain” of the smartphone, and a better name for it is the “System on a Chip” that includes elements like the CPU (Central Processing Unit), the GPU (Graphic Processing Unit) and video encoders, camera operators, audio microchip. It can also have more than one “core,” and then it will work faster, but only as fast as the Gigahertz speed. Ghz can go up to 2.4 or more. One Hertz is one cycle per second. One Gigahertz Means 1 000 000 000 cycles per second. A phone with 1 GHz speed can do one billion tiny tiny things every second.

1.3 GHz is a minimum, a slower processor will take time to load the ODK, a faster one (higher number) will work faster.

Hard Drive

16 Gigabyte – the important thing to know is that there MUST be AT LEAST (1) full Gigabyte free . . . the ODK and maps take up half of this, and there needs to be some more free as well. (This means you can’t fill up the rest with games etc.)

Some of this information can be found in SETTINGS > ABOUT PHONE

You can find out how much memory is used / available by checking SETTINGS > STORAGE AND USB

Battery Strength

milliAmpere-hours (mAh)

A quick way to think about mAh is as if it is the size of a gas tank . . . if you have a bigger gas tank, you can go further, but if one motorcycle’s engine is spending more gas than another, one tank will run out before the other.

If you have lots of apps that stay open, they can use up the battery faster. Video and games can use up a battery faster. When your screen is lit, it uses energy, when you use a flashlight app, it uses a lot of energy.

3000 mAh . . . this is quite a strong battery, and lasts better, but if your battery has a smaller number, it just means you need to recharge sooner . . . but on the motorcycles, that is possible using the motorcycle charger. Red clip to positive on the motorcycle battery, black clip to the negative post on the motorcycle battery.

(Those instructions refer to Android version 6, which is very recent . . . your phone may be different if it has a different Android number (the program that runs the phone). FIND OUT how it works, and get the answers!


September 12, 2017

Ramani Huria

Dar Es Salaam Drain Mapping Project

Humanitarian Open Street Map

Ardhi University


Each phone used must be Android AND Registered. (If for some reason, you bring a new phone, you must register that one. No unregistered phones should send surveys).

Only Android phones can be used—iPhones and Window phones do not work with ODK.

Your phone must have 1 Gb free memory to accommodate the software.

[Phone Settings]

Location Services    ON

Date and Time          USE NETWORK PROVIDED TIME

Browser                     SET TO GOOGLE for Special Drainage Update Website



3 DOTS on top right corner gives access to

General settings and Admin Settings

[General Settings]

Server                                    set to appropriate address

User Interface           ok, leave as is

Form Management 

Should be set according to your project—

If you leave Autosend OFF, remember to send your forms!

If you turn Autosend ON, you won’t be able to proofread after you mark it complete—proofread before you mark “Complete.”

Delete after Send—UNCHECKED

Other Settings are usually not relevant, just keep the defaults

User and Device Identity—leave as is

[Admin Settings]

These can be left as they are, unless there are specific instructions for your project.

In the Main Menu Settings, it is possible to hide the option in the main ODK menu that asks if you want to “Delete Forms after Sending.” HIDING would help to ensure forms couldn’t be deleted by accident.

In the User Settings, various options exist that can change the way ODK options look to the user.

The Form Entry Settings provide similar options.


Apps to install on phone

OsmAnd                   Open Street Map for ANDROID

The free version of OSM provides 7 downloads. You will need to choose the map for your working area.

[Google Maps]

WhatsApp                 Ask Administrators of groups to add your number.

Set your notifications so you can see a banner and hear when someone sends a message so that your team can communicate.

Phone Battery          Arrive fully charged, make use of Battery Packs if available.

Phone Credit            Make sure your phone has enough credit to use the apps and send data.

Close Apps when you can to save battery, but use what you need.

[Crew Leaders]


Decide upon location for meeting in the morning at 8:55am.

Not a time to go to breakfast—have breakfast BEFORE


Phone / Scratch Cards

Printed Maps / Also Maps on WA

Rod / Tape Measure / Safety Vest

Pens for marking maps and receipts / Paper for notes

Identification Card / Letter of Introduction

Shoes / Proper Clothing for the job / Food and Water / Small backpack


Helpful to other team members

Aware of the connections—no missing sections or points

Friendly to the public if people are concerned, worried, or interested

Treat Guests and Visitors with care.

Show up on time, be a professional surveyor


Practice True Leadership

Drain Mapping

Our REAL GOAL, the BIG GOAL is to save lives and improve Dar Es Salaam.

The WAY WE DO THIS is to Map drain systems, get the information to the computers so the GPS lines can be straightened, and then have that information go to the hydrologic engineers so they can recommend the best improvements and repairs.


Learn the Forms, and always report places the form does not help to survey and provide the information accurately.

Map drain systems—each section should be done from the lowest to high point.


A point, with information (Can also be a Special Comment)


A series of lines (ONE line is between 2 points, a polyline connects 3 or more points.)


A drain system can be analysed when all the points and lines connect back to a river, or natural watercourse. (Large manmade excavations for drainage are still called drains, for example the drain at the edge of Menzesi Ward.

(Also if the water goes into a place it does not drain away from—a low spot).

So our surveying is complete when the GIS team receives all the field surveys to show them how the water is going from the high points ALL the way to the ocean or rivers COMPLETELY CONNECTING.

Any time something is missed, it needs a repair. Any time the GIS team has a question, the Survey team will have to make a return visit.

“What do we do about streets that have no drains?” Either a segment should be taken or else a Special Comment should be made to show clearly that the road has been looked at—if there is NO SURVEY, it looks like no one has noticed it, and then a return visit is needed.

“What about points where drain begins, or just stops, or goes into private property?” Those points should each get separate survey completed to explain to the GIS team what is going on at that point.