Coordinates, CRS and map alignment

Qualified pilot · reviewed 19 September 2026. ArrayBridge now supports a bounded horizontal raster conversion workflow. This guide distinguishes changing a map’s display from creating new scientific data.

Three coordinate systems to keep separate

Coordinate system	What it describes	Who chooses it
Source CRS	The meaning of coordinates in the original asset	The source and its metadata
Representation CRS	The coordinates of the delivered GeoTIFF	An explicit connector conversion policy
QGIS project CRS	The coordinates used to display layers together	The QGIS user

A source can use longitude/latitude (EPSG:4326), a delivered raster can use Web Mercator (EPSG:3857), and QGIS can display both in a project using EPSG:4326. These are separate settings. ArrayBridge respects the existing QGIS project CRS; it does not change it to match an incoming layer.

Original asset                  Delivered representation          QGIS display
EPSG:4326                       EPSG:3857                         Project EPSG:4326
longitude / latitude   ----->   resampled raster         ----->   aligned map layers
                       explicit conversion              display transformation
                       original retained                stored raster unchanged

Assigning a CRS label is not converting coordinates. Relabelling local coordinates as latitude/longitude puts data in the wrong place. An unknown CRS stays unknown. The pilot refuses to import an unknown-CRS map into a geographically referenced project; its separate synthetic demo uses an unreferenced engineering project.

Display changes versus data changes

Action	Effect	New project asset revision?
Change QGIS project CRS	QGIS redraws layers in the selected coordinates	No
Rescale live colors	Fit the live layer’s color range to its current values	No
Choose a different delivery CRS, resolution or resampling policy	Create a different derived raster representation	No, when the source publication is unchanged
Publish changed source values or a new source grid	Store a new scientific snapshot; follow can advance	Yes

Colors stay fixed across live updates until you rescale them, allowing meaningful comparisons over time. A changed value can therefore look similar, or fall outside the previous color range. Check the displayed revision and numerical range before assuming an update was missed.

What conversion preserves—and what changes

Original source data remains available. The derived GeoTIFF has its own manifest with source hashes, target grid, transformation, software versions, missing-value count and declared losses. Keep the manifest with the raster when sharing it.

Reprojection usually changes sample locations and sample count. Nearest neighbor selects existing sample values. Bilinear interpolates values and is only allowed for continuous data; categorical codes require nearest neighbor. Missing samples remain missing rather than becoming zero, although the new grid can have a different missing-value count.

Horizontal coordinates and scalar values have separate units. Converting longitude/latitude to meters does not convert porosity to meters or change an elevation’s vertical datum. The public elevation fixture retains source-declared NAVD88 heights in meters, positive upward. No vertical correction is performed.

Current supported boundary

The conversion component accepts explicit two-dimensional geographic or projected CRSs sharing the same geodetic CRS. Target resolution and resampling are mandatory. Datum changes, dynamic coordinate epochs, compound/3D/vertical transformations, implicit unit changes and unknown source CRSs are refused. The pilot bounds both source and output reprojection grids to 100,000 pixels; it is not qualified for large rasters.

The source adapter must supply trustworthy CRS metadata. ResInsight project-CRS autodiscovery is not implemented. The public USGS fixture tests geographic handling independently of the synthetic ResInsight PORO workflow; it does not turn the synthetic map into geographic field data.

Non-spatial time series do not need raster reprojection. A production record may still reference a spatial well or facility, whose location requires its own CRS. Route transformations by data type rather than applying them to every asset.

Try the public-data exercise · Troubleshoot map updates · Developer contract.