Visualizing Geographic Data


Please my question: Is the values of these variable constant like is it always like this? If, No were did you generate the values from

Hi @oriji.sandra

Well those are coordinates wich not always are like that. There are different types of coordinates systems as you can read here and here. According to the basemap documentation

For the cylindrical projections ( cyl , merc , mill , cea and gall ), the default is to use llcrnrlon=-180,llcrnrlat=-90, urcrnrlon=180 and urcrnrlat=90).

So here we are using just the “default” coordinates that the API needs to create a map. If i understand correctly you always need to use those create the basemap

Hope this helps to understand
Good luck!

@alegiraldo666 My confusion is in the values llcrnrlon, llcrnrlat, urcrnrlon and urcrnrlat carry.From your explanation do you mean that -180 is the default setting of llcrnrlon, -90 is the default setting of llcrnrlat same goes to the order variable/features. Does that mean that these variables can we twerked like can be changed or Is it fixed. I read the documentation and scan through the link you recommended yet, i am not yet cleared.

Apologizes if i am disturbing.

No problem at all

The documentation says

For all other projections except ortho , geos and nsper , either the lat/lon values of the corners or width and height must be specified by the user.

So it depends of the projection you are going to use, in this case we use the merc projection so we use the default ones. In case we use ortho then could use lon_o = -90, lat_o = 0 (if i’m not mistaken i never used SIG or coordinates back on college but i shoud have :stuck_out_tongue_winking_eye:)

Thanks @alegiraldo666 for your time. I got it now :grinning: :+1: