0

I'm working on a project with a few publicly available datasets. One of them is from the USGS, it's their prediction of peak ground acceleration in 50 years. Here's a link, and here's what it looks like loaded into QGIS:

enter image description here

The problem is that the "coordinates" of San Diego, California are (roughly) -1,700,000 by 3,000,000.

The real data I'm working with is stored in SQL Geography, in a SQL Server, with SRID 4328 matched up real-world latitude and longitude.

My question is, especially since I've seen a lot of this type of who-knows-geometry going on, how do I mesh up geography with weird geometry? I'm using OGR2OGR to convert from shapefiles, in this case.

  • It's unlikely the USGS wouldn't say what projection was being used. If you edit the question to add a link to the data, or include the projection file (.prj) content, it will be easier to help you. – Vince Sep 25 '14 at 17:08
  • @Vince link added in the question, and here for reference: earthquake.usgs.gov/hazards/products/conterminous – Eric Sep 25 '14 at 17:50
  • @Vince in this question ( gis.stackexchange.com/questions/30613/… ) it's stated that QGIS will read the .prj file automatically when it loads the shapefile. It's in the right directory, I'm looking at it with notepad open. So now I have the projection, but curious why QGIS didn't set it up that way from the beginning and went with project defaults. – Eric Sep 25 '14 at 17:59
1

That data appears to be in the following coordinate system based on the files I found here.

You need to reproject/transform all of your data to be in the same coordinate system, whether it be on the fly in GIS software, or permanently in the data itself.

Clarke_1866_Albers

Authority: Custom

Projection: Albers, False_Easting: 0.0, False_Northing: 0.0, Central_Meridian: -95.0, Standard_Parallel_1: 29.5, Standard_Parallel_2: 45.5, Latitude_Of_Origin: 0.0, Linear Unit: Meter (1.0)

Geographic Coordinate System: GCS_Clarke_1866

Angular Unit: Degree (0.0174532925199433), Prime Meridian: Greenwich (0.0), Datum: D_Clarke_1866, Spheroid: Clarke_1866, Semimajor Axis: 6378206.4, Semiminor Axis: 6356583.799998981, Inverse Flattening: 294.9786982

  • thanks, I think you've got me on the right track. I'm in QGIS trying to set the projection for the layer but can't seem to find the one referenced there. – Eric Sep 25 '14 at 17:51
  • The definition is not in EPSG nor it is an Esri one. – mkennedy Sep 25 '14 at 19:53
  • Why the USGS is distributing data using the Clarke 1866 datum is beyond me... I understand using the Albers projection, but not sure why they couldn't use the NAD83 or WGS84 datums to be consistent with most other data sources. – jmpreiks Sep 25 '14 at 22:11

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.