California/Using CPAD data

From OpenStreetMap Wiki
Jump to navigation Jump to search


The California Protected Areas Database (CPAD) data published by GreenInfo Network, downloadable from here and noted in our Contributors page are slowly but surely being incorporated into OSM: not as an import, but more-or-less curated one polygon at a time on a case-by-case basis. These data might be almost anywhere in the state, but curated CPAD data are now (2019 and later) found in Santa Cruz, San Mateo and Santa Clara counties. CPAD includes all "protected as permanent open space lands in California:" 15,000 parks and preserves owned by over 1,000 agencies/organizations.

Data format

CPAD is made available as three kinds of data agglomerations: SuperUnits (high-level), Units (medium) and Holdings (at a fine-grained, almost "individual parcel" level). See the CPAD data pages to determine which one might be appropriate for your use. SuperUnits might be best for an initial "wide scale" view of the data, so start there. If OSM desires greater detail, the Units and Holdings shapefiles might be used. Each of these are a zipped shapefile. To open them, unzip the "data glom" you will use, have the opendata plugin installed into JOSM and use JOSM's "open file" on the .shp (shapefile).

From CPAD 2019b, here is a typical single-item datum (part of an Open Space Preserve in Santa Cruz) as the various tags found on the polygon:

ACCESS_TYP=Open Access
AGNCY_NAME=Santa Cruz, City of
AGNCY_TYP=City Agency
CITY=Santa Cruz
COUNTY=Santa Cruz
DES_TP=Local Conservation Area
MNG_AGNCY=Santa Cruz, City of
SITE_NAME=Pogonip Open Space Preserve
UNIT_NAME=Pogonip Open Space Preserve

That's a lot of data! Most of these are "internal to CPAD" and don't logically map well to any specific OSM tags. Some, however, do. Others, especially UNIT_ID and ACRES are useful to include in the data: UNIT_ID is useful as it allows a unique identifier from CPAD, and ACRES is useful as a sort of "checksum" of the data. What is meant by "checksum" is that a particular datum might change from version to version of CPAD, but this might be a very small or subtle change and isn't readily apparent or easily visually identifiable. But if there is a change between CPAD versions, the ACRES value will almost certainly change, especially out to one of its many digits of precision.

Generally area sizes from shapefiles should not be incorporated into OSM. Please see the Talk page for Discussion about this.

Suggested tag-migration protocol

So, which tags to keep, which to delete? Here are suggestions:

CPAD Tag Action New OSM key=value
ACCESS_TYP Keep Change to access=*. If "Open Access" set value "yes" if "Restricted Access" set value "private" if "No Public Access" set value "no" if "Unknown" set value "unknown"
ACRES Special Change to cpad:acres=* with the same value. If multiple "sub-units" are coalesced to form a larger unit, delete these differing ACRES tags.
AGNCY_LEV Keep Change to ownership=*. If "Federal" set value "national" if "State" set value "state" if "County" set value "county" if "City" set value "city"
AGNCY_NAME Keep Change to owner=* with the same value
AGNCY_TYP Special Usually, delete this, but see DES_TP, below
AGNCY_WEB Special Change to website=* with the same value, unless there is a PARK_URL which differs (if so, delete this tag and see PARK_URL). If empty, delete.
CITY Delete
DES_TP Optional If you wish, and it distinctly adds clarity to "what this is," change to description=* with the same value. If you include AGNCY_TYP here, too, semi-colon separate the values.
GAP_STS Delete
LAYER Delete
MNG_AGNCY Keep Change to operator=* with the same value
MNG_AG_ID Delete
PARK_URL Special Change to website=* with the same value, unless this value is empty, then set AGNCY_WEB to website=* instead
UNIT_ID Special Change to cpad:unitid=* with the same value. If multiple "sub-units" are coalesced to form a larger unit, delete these differing UNIT_ID tags.
UNIT_NAME Keep Change to name=* with the same value
YR_EST Delete
YR_PROTECT Special If 0 (zero), delete. If non-zero, change to start_date=* with the same value

Add an additional OSM-specific "physical" tag, like leisure=nature_reserve or boundary=protected_area (plus the proper protect_class=* value). The choice of which tag(s) to add is at the discretion of the author, but do strive to tag consistently with documented uses. See (the emerging wiki) United_States/Public_lands for additional suggestions: these are intended to follow regularized tagging protocols as documented there.

Applying these suggestions, this results in the following tags on the polygon in OSM:

description=Local Conservation Area
name=Pogonip Open Space Preserve
operator=Santa Cruz, City of
owner=Santa Cruz, City of

In this specific example, other sub-unit polygons were coalesced together to form a larger cohesive unit, so there are neither cpad:unitid=18677 nor cpad:acres=492.2348748251647 tags. If this were an isolated (multi)polygon, there would be these tags.

Some might explicitly add source=CPAD 2019b to each datum, but it is a more modern convention to enter this on the entirety of the changeset during upload (JOSM has "Specify the data source for the changes"), where this may simply be set to "CPAD 2019b" (for example).

Extraneous data found in OSM

Sometimes shapefile tags in ALL CAPITAL LETTERS are left in the data when they do not logically map well to OSM tags. Where objectionable, these tags can be deleted from OSM. However, for the reasons indicated above, please leave intact (older) tags of ACRES and UNIT_ID.