Opened 13 years ago

Last modified 11 years ago

#1372 new enhancement

Different lat-lon grid size for geographic grids

Reported by: alf Owned by: grass-dev@…
Priority: normal Milestone: 6.5.0
Component: Display Version: svn-develbranch6
Keywords: d.grid Cc:
CPU: Unspecified Platform: All


When setting locations at high latitudes, the meridians / parallels spacing ratio tend to be small. Find attached an example of a lcc grid with projection at high lats (lcc_geogrid.png).

In order to have a better output we could introduce parameters for optional separate ew and ns (geo)grid sizing.

Also it will be important to set a minimum/maximum for grid drawing, so we can avoid cluttering the maps as soon as meridians become too dense (e.g. in polar areas).

Alessandro Frigeri

Attachments (1)

lcc_geogrid.png (7.6 KB ) - added by alf 13 years ago.
Geogrid for lcc projection at high latitudes: effect of a single 'size' parameter for geogrid

Download all attachments as: .zip

Change History (6)

by alf, 13 years ago

Attachment: lcc_geogrid.png added

Geogrid for lcc projection at high latitudes: effect of a single 'size' parameter for geogrid

comment:1 by hamish, 13 years ago

Keywords: d.grid added

comment:2 by hamish, 13 years ago

Component: Projections/DatumsDisplay
Milestone: 6.5.0

work around: run d.grid at the desired longitude spacing, and then again with the grid size set to the latitudes you want grid lines at.

so for your example:

d.grid -g size=2
d.grid -g size=86:12
d.grid -g size=86:18


comment:3 by hamish, 11 years ago

btw, I just fixed d.grid + geogrid longitude label placement in all branches for meridians which deviated to grid-north by many degrees (e.g. zoomed-out LCC projections).


comment:4 by hamish, 11 years ago

new direction= option added in devbr6 r57699 to allow only drawing east-west or north-south grid lines. run the module twice with two different size intervals to get the custom effect. I'll try to find a few minutes to port it to g7 in the morning.

for drawing fiducial marks it would be better to have the size= option optionally take a second parameter, but I don't like overloading the parameter definition like that very much, and adding two new size_ew= and size_ns= options like g.region does for res= clutters the option list and Required-> parser setting, so isn't great either.

happy to entertain better ideas..


comment:5 by hamish, 11 years ago

merged into trunk in r57714.

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