Description of GRB data types and usefulness for OSM.
- Adp: Administrative parcels: Not useful due to convention that these don't belong in OSM
- Ano: Anomalies (mistakes and new developments): should be used together with other data types, to see if a new development is happening or a mistake is reported
- Gba: Building attachment: Partially useful for OSM:
- afdak : building=roof
- loopbrug: ??? pedestrian, mostly covered bridge connecting two buildings (can be found between high office towers or in factories)
- trap : ??? a stair area connected to a building (like in front of an entrance of a big building)
- zichtbare onderkeldering : No idea what this is
- ingezonken garagetoegang : ramp of a garage entrance below ground level
- uitbreiding : AFAIK, a regular building=*
- verheven garagetoegang : ramp of a garage entrance above groun level
- verdieping: building that's not on the ground (so you can walk below it), but not a roof either.
- Gbg: Regular building (GeBouw aan de Grond, building on the ground)
- Gvl : The building sides split up by measurement method used (measured from the street, from imagery, estimated, ...) can be useful to deduce the quality of the buildings, but not wanted in OSM.
- Gvp : point of a building with annotated measurement method. Not useful for OSM.
- Knw : Different man-made objects
- overbrugging : man_made=bridge
- waterbouwkundige constructie : In the extract I used: bogus data
- cultuurhistorisch monument : Small elements, most likely chapels, but there's no subdivision
- hoogspanningsmast / openbare TV-mast : power=tower or man_made=mast
- pijler : ???
- rooster : ???
- schoorsteen : chimney man_made=chimney
- koeltoren : man_made=tower + tower:type=cooling
- silo, opslagtank : storage tank man_made=storage_tank or man_made=silo
- cabine : Electrical, gas or other cabine
- watertoren : water tower man_made=watertower
- tunnelmond : tunnel exit, probably doesn't belong in OSM
- chemische installatie : Chemical installation ???
- golfbreker (strandhoofd en lage havendam) : man_made=groyne (perhaps also man_made=breakwater)
- havendam : man_made=breakwater
- staketsel : man_made=pier
- Lbz : zones used for internal management of GRB, no use in OSM
- Sbn : railway area landuse=? (split per type of usage: train, tram and metro)
- Trn : public terrain that doesn't fall under highway area (mostly unregulated parking space). Very sparse data, so not useful for an import
- Wbn : highway area landuse=* every crossing is a different area, so it uses the "plumbing" principle, but it overlaps other landuses where separation isn't clear (in rural areas). Slightly over-noded, possibly not suited for import.
- Wga : highway-related feature
- Wgo : highway border per usage type (no areas, but the borders can be combined to areas)
- grens circulatiezone zwakke weggebruiker (Wcz) : boundary of the pedestrian area (not every way has this, cannot always be close)
- rand van de rijbaan (Wrb) : boundary of the motorised area (most inner boundary, can always be closed)
- grens onverharde zone (Woz) : boundary of the paved zone (cannot be closed, is cut at every place where a private paved area touches a highway - like a service way or path), probably not suited for import
- Wgr : ditch waterway=drain (not oriented in a meaningful way)
- Wkn : way knode (endpoint of a way), only one case is useful:
- Wni : lenghtwise highway element
- Wpi : pointshaped highway element
- paal : pole, mix between highway=street_lamp and man_made=power_pole, sometimes both
- meerpaal : mooring pole
- bovengrondse brandkraan : fire hydrant (above ground) emergency=fire_hydrant
- grenspaal : boundary stone historic=boundary_stone
- praatpaal, paal met publieke telefoon : emergency phone emergency=phone
- Wri : manhole covers manhole=* ?
- Wrl : railway when crossing the highway: too restricted for OSM
- Wti : transversal highway feature (lower edges of a traffic_calming=table/bump/hump or upper edge of a road lowering (inversed table))
- Wtz : water area natural=water, these are tagged a lot wider than the average upper water level, and often include the grassy riverbanks. So perhaps not suited for import due to differing definitions
- Wvb : highway=motorway/trunk/ ... /service/track Follows the center line, and contains the following info about the road.
- Left and right name (equal in most cases) : name=*, name:left=* and name:right=* (left and right aren't needed in OSM when they are equal)
- National reference ("ng" means no reference) : ref=*
- Left and right municipality name (equal in most cases, unequal on boundaries) : not needed in OSM
- surface (paved or unpaved): surface=* (though more difersity is sometimes wanted in OSM)
- road class, choice among:
- autosnelweg : highway=motorway
- weg met gescheiden rijbanen die geen autosnelweg is : highway=trunk or highway=primary
- weg, bestaande uit één rijbaan highway=primary/ ... / track
- rotonde highway=* + junction=roundabout
- speciale verkeerssituatie : ???
- verkeersplein : ?? pedestrian highway ??
- op- of afrit, behorende tot een niet-gelijkgrondse verbinding : highway=motorway_link or highway=trunk_link
- op- of afrit, behorende tot een gelijkgrondse verbinding : highway=*_link
- parallelweg : highway=tertiary/unclassified/service
- ventweg : same as parallelweg?
- in- of uitrit van een parking : highway=service + service=parking_aisle
- in- of uitrit van een dienst : highway=service
- wandel- en/of fietsweg, niet toegankelijk voor andere voertuigen : highway=path/footway/cycleway (though most are unmapped)
- tramweg, niet toegankelijk voor andere voertuigen | railway=*
- dienstweg : highway=service
- Wlas : streams and rivers (everything wider than 3m) with name and name of watershed
Quality of GRB data
GRB building data has two quality levels: measured and drawn from aerial imagery.
- The measured data is always very precise (more precise than anything we can achieve), but may be outdated a few months.
- The data derived from aerial imagery is about as good as we can achieve in OSM with mapping from correctly aligned pictures.
In general, everything that can be measured from public roads is also measured. So the front sides of the buildings are measured, the back sides aren't.
The GRB buildings data seems to have around 10% useless nodes. This mostly comes from their measurement process. If they can't measure a back corner of a house, they measure a point in the side wall. That measurement point is then used to map the rest from imagery. But that measurement point is always on a straight line, so useless to OSM.
As the difference made by the node to the shape is always very close to zero (the only difference is a rounding error), it's easy to delete these nodes with the simplify-area tool from JOSM (a plugin) using very strict settings (1m deviation, 10° angle, 3m² area f.e.).
Combining with CRAB data directly
According to the documentation, a GRB-to-CRAB table is included for certain data types so all buildings with addresses also have that info (In a .dbf file. This file name starts with 'Tbl' and then the datatype follows and then 'Adr' . ex: TblAdpAdr46024B500.dbf and TblGbgAdr46024B500.dbf ) It makes the process a lot easier, though we must also still take the errors in CRAB into account (which is why the CRAB import has been done manually so far). These addresses do not always match with AGIV, hence it's important to use these on buildings that haven't got any addressing yet. We should still use the CRAB import tool to correct and review this data later on. Luckily, this tool has quality indicators on board to monitor completeness.