Increasing detail in pscoast

Added by Bob 10 months ago

I ran pscoast (pscoast -R-85/-84/45.5/46.1 -JM14i -Df -P -Ia1 -Ba -Wthinnest -Glightgray -Slightblue -TdjRB+o2i/2i+w1i+f3+lW,E,S,N > GMT_Straits.ps) for the Straits of Mackinac in Michigan recently and found that even with the -Df option the resolution of the coastline was off significantly. I noticed one fairly large bay in particular was not showing up, did a google map for the same region and when I overlay it and the GMT output there were significant differences.
Is a finer resolution available or is this as fine a detail as GMT can do? I have looked through the documentation and this forum but haven't seen any information pertaining to this.

Thanks for your help


Replies (3)

RE: Increasing detail in pscoast - Added by Paul 10 months ago

GMT relies on GSHHG which derives from free datasets from the 1980s. There is considerable offsets when zooming in "too far". The GSHHS data is good for regional-type studies but breaks down at your scale. In addition to small features missing there may also be misregistration by several hundred meters to a km due to cumulative errors from digitizing, datum confusion, format confusion, etc.

RE: Increasing detail in pscoast - Added by Bob 10 months ago

Thanks for the information. I located some information on using Shuttle Radar Topography Mission (SRTM) data in GMT to get finer details. I'll try that option out and see what that looks like.

RE: Increasing detail in pscoast - Added by John 10 months ago

What I've done is to take a high-resolution bathytopo and generate a 0 m contour with grdcontour and use that as the coastline.

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