Overview

This is a follow-up to a recent post about an issue affecting the import of geometry data in Alloy Web.

The issue was caused by a third-party service (espg.io), which provided Alloy with a list of Coordinate Reference Systems (CRS) and the corresponding proj4 strings required for converting the incoming geometry data accordingly. Upon discovering the issue, we quickly issued a temporary workaround.

To avoid this situation repeating in future, we’ve now removed this dependence from Alloy in favour of a curated local list.

Who will be affected?

This change affects all users who use Gateway to import geometry data in Alloy Web.

Details

When configuring an import in Alloy, there are two optional steps in the procedure that involve imported geometry:

• Attributes – in this step, you can map headers in the incoming data to attributes on the selected design. After selecting a GeoJSON attribute, you can select the Coordinate System field and choose one from the list (see below).
  
  
• Geometry – in this step, you can specify the type of geometry data to be imported. After selecting a Type, you can select the 🔍 icon in the Coordinate System field and choose one from the list (see below). Unlike the previous step, the full proj4 string will appear in the field, so it can be edited if necessary before selecting Done.

The coordinate system will default to WGS84 Lat/Lng if not explicitly set.

If you have any existing imports that include geometry data and have a Status of Configured or Validated, we recommend reconfiguring them. To do this, open the import item, select More in the bottom action bar and choose Reconfigure.

Available Coordinate Systems

We’ve included the most popular coordinate systems to choose from. Any others we should add? Please feel free to contact Support with your suggestions!💡

OSGB36 / British National Grid
SRID:27700
+proj=tmerc +lat_0=49 +lon_0=-2 +k=0.9996012717 +x_0=400000 +y_0=-100000 +ellps=airy +towgs84=446.448,-125.157,542.06,0.15,0.247,0.842,-20.489 +units=m +no_defs

WGS84 Metres
SRID:3857
+proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0 +k=1.0 +units=m +nadgrids=@null +wktext  +no_defs

WGS84 Lat/Lng
SRID:4326
+proj=longlat +datum=WGS84 +no_defs

NZGD2000 / New Zealand Transverse Mercator
SRID:2193
+proj=tmerc +lat_0=0 +lon_0=173 +k=0.9996 +x_0=1600000 +y_0=10000000 +ellps=GRS80 +towgs84=0,0,0,0,0,0,0 +units=m +no_defs

Expected Release

Due to this new feature’s importance, it was hotfixed into the current Alloy v2.40 release on 17th October 2022.