Coverage grid coordinates don't match survey region extent

[LHMarshall]

We have found that for a specific projection (there may be others) that Distance doesn't seem to be correctly interpreting the projection information. The study area is imported and displays fine but when asked to create a coverage grid the coordinates of the coverage grid do not fall within the study region (this can be checked by creating a map and adding the study area and then the coverage grid - you should see the coverage grid points across the study area). This problem persists whether the shape import wizard is used or whether they are manually imported by copying them into the .dat folder.

We often recommend that projection information not be included in Distance projects once the shape file has been projected into m, km etc. So a simple fix is just to separate the .prj file from the shape file prior to import. You need only then tell Distance which units are correct for your study region. You can then reattach the .prj file to the study region later and any surveys created in Distance to back transform into lat and lon in your GIS software.

Note that dssd our design package in R did not display the same issues with the problematic projection as seen in Distance so this is another alternative.

It is unlikely that we will be able to resolve this issue from within Distance.

[lenthomas]

In case it's helpful, there's a Tip about how to bypass projections in the Distance for Windows help, Chapter 5, under "Coordinate Systems and Projections". Within that, in the page titled "Coordinate systems, maps and calculations in Distance" it says:

Tip: P
rojecting data takes time. This can significantly affect the performance of survey design calculations, such as calculating coverage probability and creating new surveys. Therefore, if you always use the same projection for a particular set of data, consider projecting the data using an external GIS package and storing the projected data in a shapefile. When you bring the data into Distance, set it as no coordinate system (you can do this by setting the coordinate system and projection to None in File | Project Properties | Geographic, and setting the units correctly, and then not copying over the .prj part of the shapefiles when you import your shapefiles – see Importing Existing GIS data). Distance will then treat the data as simple x,y coordinates and will not spend time projecting and re-projecting it.