Increasing detail in pscoast

Added by Bob 7 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 7 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 7 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 7 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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