Every grid the converters use, where it came from, and what the license permits.
Publishing these tools redistributes the underlying geometry, which is a different
permission from displaying it inside our own app. Each entry below is recorded against
that stricter test.
Built by scripts/grid-tools/ from files in /Volumes/Workspace/SurveyArk/Shapefiles/.
| Dataset | ATS v4.1 Polygons — Quarter Sections (`ATS_Polygons/.../V4-1_QTR.shp`) |
|---|---|
| Publisher | Government of Alberta |
| Distributor | AltaLIS Ltd., on behalf of the province |
| Source | https://open.alberta.ca/opendata/property-alberta-township-system-ats |
| License | **Open Government Licence – Alberta** |
| Redistribution | **Permitted**, including commercially, with attribution |
| Attribution (required) | *Contains information licensed under the Open Government Licence – Alberta.* |
| Datum | NAD83 (EPSG:4269), converted to WGS84 |
| Coverage | 1,018,779 quarter sections in 7,196 townships |
Note on AltaLIS. AltaLIS distributes the same ATS data through both an open channel and
a commercial one. This build uses the open channel. The commercial product carries different
terms and must not be substituted.
Township grid, separately. ST37_WG_* carries embedded metadata naming the
Alberta Energy Regulator as the source. Not used by the converters, which derive
townships from the quarter data, but recorded here since it sits in the same folder.
| Dataset | BC NTS Grid, quarter units (`BC-NTS-GRID/6-BCNTS-Quarter.gpkg`) |
|---|---|
| Base data | NRCan "Indexes of the National Topographic System of Canada" — open.canada.ca dataset `055919c2-101e-4329-bfd7-1d0c333c0e62` |
| Publisher | Natural Resources Canada |
| License | **Open Government Licence – Canada** (verified 2026-08-07) |
| Derivation | Mark clipped the BC extent in QGIS; block/unit/quarter tiers are the regular NTS subdivision computed from the index sheets |
| Attribution (required) | *Contains information licensed under the Open Government Licence – Canada.* |
| Datum | NAD83 (EPSG:4269), converted to WGS84 |
| Coverage | 5,055,469 quarter units in 13,330 sheet-blocks |
✅ Resolved 2026-08-07 (Mark identified the source; license verified on the record).
| Dataset | Quarter Section DLS Grid — Peace River Block |
|---|---|
| Publisher | BC Energy Regulator (BCER) |
| Source | BCER Open Data Portal — Township Range / Section / Quarter Section DLS PRB |
| License | BC Energy Regulator Open Data Licence |
| Redistribution | Permitted, including commercially, with attribution |
| Attribution (required) | Contains information licenced under the BC Energy Regulator Open Data Licence. |
| Datum | NAD83 / BC Albers (EPSG:3005), converted to WGS84 |
| Coverage | 21,827 quarter sections in 180 townships |
The grid's custodian is the Surveyor General Division of the Land Title and Survey Authority of BC; the BCER publishes it as open data.
| Dataset | BLM National PLSS CadNSDI (`BLM_NATL_PLSS/ilmocplss.gdb`) |
|---|---|
| Layers | `PLSSTownship` (85,983), `PLSSFirstDivision` (2,773,681) |
| Publisher | US Bureau of Land Management |
| Source | https://www.blm.gov/services/geospatial/PLSS |
| License | **Public domain** — a work of the US federal government |
| Redistribution | Permitted without restriction; attribution as a courtesy |
| Datum | Web Mercator (EPSG:3857), converted to WGS84 |
| Coverage | 2,747,128 sections in 82,558 townships, 30 states |
26,552 section rows were rejected: their township id does not resolve, or the section number
is not numeric. That is 0.96% of the layer and it is source data quality, not a build fault.
| Dataset | OTLS digital map data (`Texas/OTLS Grid/survALLp`) |
|---|---|
| Publisher | Railroad Commission of Texas |
| Source | https://www.rrc.texas.gov/resource-center/research/digital-map-information/ |
| License | Public RRC GIS services (verified 2026-08-07: the same `gis.rrc.texas.gov/server/rest/services/rrc_public` endpoints the SurveyArk platform's monthly auto-refresh consumes — data the commission publishes for programmatic use) |
| Datum | **NAD27**, datum shift applied to WGS84 |
| Coverage | 311,285 surveys across all 254 counties |
✅ Resolved 2026-08-07. The RRC serves this data from its public ArcGIS REST services
(rrc_public/RRC_Public_Viewer_Srvs, rrc_public/tpms), which SurveyArk already consumes for
monthly refresh of surveys, pipelines, wells, counties and districts.
County names come from the US Census Bureau national county file
(national_county2020.txt), which is public domain. The survey layer itself carries no county
field; the FIPS code is recovered from MERGE_SRC.
NAD27 matters here. NAD27 and WGS84 differ by roughly 100 m in Texas, which is far larger
than a survey boundary. The shift is applied at build time. The Canadian grids are NAD83, within
a couple of meters of WGS84, and are converted anyway so everything reports in one frame.
Saskatchewan. Behind a paywall. Excluded deliberately, and the same reasoning would apply
to any commercially licensed grid.
Correctness is measured against ground-truth points taken from the source datasets with GDAL,
not against the packs themselves. scripts/grid-tools/sample_truth.py samples real features and
takes a point guaranteed to lie inside each; scripts/grid-tools/verify.mjs runs those points
through the same client code the browser loads.
| Grid | GPS → grid | Round trip |
|---|---|---|
| Alberta | 300/300 | 300/300 |
| BC NTS | 300/300 | 300/300 |
| BC DLS | 200/200 | 200/200 |
| PLSS | 399/400 | 400/400 |
| Texas | 297/300 candidates contain the true survey | 256/300 unambiguous |
The PLSS miss is a source row whose section number is not a number. Texas is discussed in
js/grid-tx.js: overlapping historical grants mean 15% of points genuinely sit in more than one
survey, so all of them are shown rather than one being chosen.