# Map up to the south pole. Bug in -R+uk? **URL:** \ **Category:** Q&A\ **Created:** [September 3, 2021, 12:18am UTC](https://forum.generic-mapping-tools.org/t/map-up-to-the-south-pole-bug-in-r-uk/2053 "2021-09-03T00:18:45Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![Esteban82](https://yyz1.discourse-cdn.com/flex047/user_avatar/forum.generic-mapping-tools.org/esteban82/32/54_2.png) [@Esteban82](https://forum.generic-mapping-tools.org/u/Esteban82)\ **Post date:** [September 3, 2021, 12:18am UTC](https://forum.generic-mapping-tools.org/t/map-up-to-the-south-pole-bug-in-r-uk/2053/1 "2021-09-03T00:18:45Z")
I want to make a rectangular map with a Lambert projection (-JA-60/-40/15c) that extends just up to the south pole (like [this map](https://www.ign.gob.ar/gallery-app/mapas-escolares/medium/argentina_bicontinental_mudo.jpg)). So I using **-R** _xmin_/_xmax_/_ymin_/_ymax_ **+u** _unit_ to define the region. So I used this to calculated the distance to the South Pole which gives 5573 km. ` S=$(echo -60 -40 | gmt mapproject -G-60/-90+uk -o2)` But I get this image. By try and error I found that I must used **-5420** to get the map that I want. Am I using the R method right? Is it a bug? ![SouthPole](https://canada1.discourse-cdn.com/flex047/uploads/gmt/original/2X/f/f0870487f06b4a33d9bd011547747aa859064096.png) ``` #!/usr/bin/env bash Lat=-40 S=$(echo -60 ${Lat} | gmt mapproject -G-60/-90+uk -o2) # Region geografica del mapa REGION=-2500/3100/-5573/2100+uk #REGION=-2500/3100/-5420/2000+uk #REGION=-2500/3100/${S}/2000+uk gmt begin SouthPole png gmt coast -R$REGION -JA-60/${Lat}/15c -Dl -W -N1 -G245/241/214 -S199/224/246 -Bg10 gmt end #show ``` ---
**Author:** ![pwessel](https://yyz1.discourse-cdn.com/flex047/user_avatar/forum.generic-mapping-tools.org/pwessel/32/30_2.png) [@pwessel](https://forum.generic-mapping-tools.org/u/pwessel)\ **Post date:** [September 3, 2021, 1:00am UTC](https://forum.generic-mapping-tools.org/t/map-up-to-the-south-pole-bug-in-r-uk/2053/2 "2021-09-03T01:00:34Z")
I think you are doing it right but GMT may not be. The conversion from your **+uk** to the equivalent **-R** … **.+r** settings in degrees takes place in _gmtinit\_rectR\_to\_geoR_ in gmt\_init.c. You can have a look and see if you notice anything funny for your case. I will have a look later once done with current PR… ---
**Author:** ![pwessel](https://yyz1.discourse-cdn.com/flex047/user_avatar/forum.generic-mapping-tools.org/pwessel/32/30_2.png) [@pwessel](https://forum.generic-mapping-tools.org/u/pwessel)\ **Post date:** [September 3, 2021, 1:36am UTC](https://forum.generic-mapping-tools.org/t/map-up-to-the-south-pole-bug-in-r-uk/2053/3 "2021-09-03T01:36:14Z")
Actually, you are using in wrong… Your measure from **mapproject** is the actual length of the curved arc along the meridian on a spherical Earth, whereas the coordinates in **-R…+uk** are distances on a flat projection of the Earth, so it depends on the properties of the projection. If I do things like this: ``` echo 0 -90 | gmt mapproject -Rg -JA-60/-40/25c -C -Fk 3.72772596975e-13 -5385.00930501 ``` and use -5385.00930501 then it looks as you expect. ---
**Author:** ![Esteban82](https://yyz1.discourse-cdn.com/flex047/user_avatar/forum.generic-mapping-tools.org/esteban82/32/54_2.png) [@Esteban82](https://forum.generic-mapping-tools.org/u/Esteban82)\ **Post date:** [September 3, 2021, 1:49am UTC](https://forum.generic-mapping-tools.org/t/map-up-to-the-south-pole-bug-in-r-uk/2053/4 "2021-09-03T01:49:40Z")
Thanks. I think -R+uk is more complex than I thought. ---
**Author:** ![pwessel](https://yyz1.discourse-cdn.com/flex047/user_avatar/forum.generic-mapping-tools.org/pwessel/32/30_2.png) [@pwessel](https://forum.generic-mapping-tools.org/u/pwessel)\ **Post date:** [September 3, 2021, 2:15am UTC](https://forum.generic-mapping-tools.org/t/map-up-to-the-south-pole-bug-in-r-uk/2053/5 "2021-09-03T02:15:29Z")
Yes, it refers to (flat) map distances, not (spherical/ellipsoidal) Earth distances. ---
**Author:** ![pwessel](https://yyz1.discourse-cdn.com/flex047/user_avatar/forum.generic-mapping-tools.org/pwessel/32/30_2.png) [@pwessel](https://forum.generic-mapping-tools.org/u/pwessel)\ **Post date:** [September 3, 2021, 2:16am UTC](https://forum.generic-mapping-tools.org/t/map-up-to-the-south-pole-bug-in-r-uk/2053/6 "2021-09-03T02:16:16Z")
You can check if the documentation is not clear. I think it does say projected distances or similar though. ---
**Author:** ![Esteban82](https://yyz1.discourse-cdn.com/flex047/user_avatar/forum.generic-mapping-tools.org/esteban82/32/54_2.png) [@Esteban82](https://forum.generic-mapping-tools.org/u/Esteban82)\ **Post date:** [September 3, 2021, 2:17am UTC](https://forum.generic-mapping-tools.org/t/map-up-to-the-south-pole-bug-in-r-uk/2053/7 "2021-09-03T02:17:06Z")
So, for example if I want a map to extend 4000 km to the south (from the standard lat and long), how should I do? ---
**Author:** ![pwessel](https://yyz1.discourse-cdn.com/flex047/user_avatar/forum.generic-mapping-tools.org/pwessel/32/30_2.png) [@pwessel](https://forum.generic-mapping-tools.org/u/pwessel)\ **Post date:** [September 3, 2021, 2:33am UTC](https://forum.generic-mapping-tools.org/t/map-up-to-the-south-pole-bug-in-r-uk/2053/8 "2021-09-03T02:33:29Z")
If you mean a real Earth distance of 4000 km then you would compute the coordinate of the point that is 4000 km to the south, e.g. ``` echo -60 -40 | gmt vector -Tt180/4000k -60 -75.9728147105 ``` and then get the flat map coordinate of that point for your chosen projection: ``` echo -60 -75.9728147105 | gmt mapproject -Rg -JA-60/-40/1 -C -Fk 0 -3934.62493195 ``` and then use that in your -R…+r. ---
**Author:** ![Esteban82](https://yyz1.discourse-cdn.com/flex047/user_avatar/forum.generic-mapping-tools.org/esteban82/32/54_2.png) [@Esteban82](https://forum.generic-mapping-tools.org/u/Esteban82)\ **Post date:** [September 3, 2021, 2:48am UTC](https://forum.generic-mapping-tools.org/t/map-up-to-the-south-pole-bug-in-r-uk/2053/9 "2021-09-03T02:48:57Z")
Ok. Thanks. I will need to study a bit it seems.