Trouble plotting wet features in small areas

Q&A
1

Using pscoast, I’m trying to fill the wet areas in blue/green. What I end up with, however, doesn’t match the reality.

gmt pscoast -R-74.0571/-73.89/40.69/40.88 -Jm20i -Baf -Wthin -Df -P -Xc -Yc -Ia -Sblue -Gred -Cgreen > output.ps

manhattan-compare
manhattan-compare1055×846 329 KB

The Hudson River should continue up the left side of the output. The Harlem River should connect the Hudson with the East River, which is present on the right side of the output.

Am I missing any options? Or is this a case where the data isn’t available, isn’t fine-grained enough, or is malformed?

Thanks.

2

GSHHG is no match for OSM. GSHHS is from the 1970-80s and pretty good for regional work but looking at small spots of land will reveal big weaknesses. In this case you are better getting your own shape files from OSM or USGS etc.

3

Looks like I can create my own shapefile from an OSM export with a variety of tools:

https://wiki.openstreetmap.org/wiki/Shapefiles#Create_your_own_shapefiles

I’m unsure of what I gain by this. Will it allow me to draw rivers, lakes, and other water forms? Will it let me fill water and land areas with color with GMT tools?

I’ve successfully used psxy to draw roads from a postgres database. Does a shapefile supplement psxy?

Any further pointers in the right direction would be great. Thanks.

4

You can indeed plot shapefiles this way, it will be treated as closed polygon (or, if memory serves me well, see L eventually). You would then assign the colour you want for each psxy line.