[GRASS-user] Scalebar for lon/lat projection in ps.map

GRASS GRASS user
1

Hi,

I am preparing a country-wide map using ps.map. The region spans 2-3
UTM zones although most of the region is covered by one zone but I
still need the data at the fringes covered in another zone. In order
to do that I used a lon/lat projection. However, ps.map will not
produce a scalebar for lon/lat projection for good reasons.

I know this isn't good practice. Any Ideas how I can produce a
"scalebar" for lon/lat?

cheers,
maning

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| __.-._ |"Ohhh. Great warrior. Wars not make one great." -Yoda |
| '-._"7' |"Freedom is still the most radical idea of all" -N.Branden|
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2

maning sambale wrote:

I am preparing a country-wide map using ps.map. The region spans 2-3
UTM zones although most of the region is covered by one zone but I
still need the data at the fringes covered in another zone. In order
to do that I used a lon/lat projection. However, ps.map will not
produce a scalebar for lon/lat projection for good reasons.

I know this isn't good practice. Any Ideas how I can produce a
"scalebar" for lon/lat?

You could change the projection to Plate Carée (aka Equidistant
Cylindrical), which is essentially just lat/lon with scale factors.

Also, there's no fundamental reason why you can't use UTM for data
which doesn't fit within a single zone (obviously, if you have data in
other UTM zones, you'll have to reproject it, but that's no worse than
reprojecting to lat/lon).

--
Glynn Clements <glynn@gclements.plus.com>

3

maning sambale wrote:

I am preparing a country-wide map using ps.map. The region spans 2-3
UTM zones although most of the region is covered by one zone but I
still need the data at the fringes covered in another zone.
In order to do that I used a lon/lat projection. However, ps.map
will not produce a scalebar for lon/lat projection for good reasons.

I know this isn't good practice. Any Ideas how I can
produce a "scalebar" for lon/lat?

my advice is: don't. overlay a grid or geogrid instead. with at least
two grid lines for both lat + long the reader can see the scale.

you can reproject everything into the central UTM zone, but the outside parts may start to be distorted. if only going +/- 1 zone you may get away with it.

Hamish

4

On 7/19/08, Hamish <hamish_b@yahoo.com> wrote:

maning sambale wrote:

I am preparing a country-wide map using ps.map. The region spans 2-3
UTM zones although most of the region is covered by one zone but I
still need the data at the fringes covered in another zone.
In order to do that I used a lon/lat projection. However, ps.map
will not produce a scalebar for lon/lat projection for good reasons.

I know this isn't good practice. Any Ideas how I can
produce a "scalebar" for lon/lat?

my advice is: don't. overlay a grid or geogrid instead. with at least
two grid lines for both lat + long the reader can see the scale.

Thanks!

you can reproject everything into the central UTM zone, but the outside
parts may start to be distorted. if only going +/- 1 zone you may get away
with it.

I followed this advice and used a central UTM zone.

Hamish

--
|---------|----------------------------------------------------------|
| __.-._ |"Ohhh. Great warrior. Wars not make one great." -Yoda |
| '-._"7' |"Freedom is still the most radical idea of all" -N.Branden|
| /'.-c |Linux registered user #402901, http://counter.li.org/ |
| | /T |http://esambale.wikispaces.com|
| _)_/LI
|---------|----------------------------------------------------------|