Hi

I have a set of records with known lat long. I want to show the concentration of the records with a contour diagram on a world map in any projection. It cannot spill over to the oceans. I know I have to use basemap. Is there a quick recipe somewhere I can follow to give me a desired output. I have gone through earlier posts on this board but cannot find the right one. Any pointers would be very helpful. Many thanks.

Best

Mitra

# Contoured basemap

Mitra: The basic procedure is this:

1) load you data into 2d numpy arrays (lats, lons, data). lats and lons must be in degrees (not radians).

2) create a Basemap instance (called "map") for the desired projection.

3) calculate the map projection coordinates of your grid with x,y = map(lons,lats)

4) contour your data with the contourf method (map.contourf).

5) draw coastlines with the coastlines method.

6) draw lat/lon lines with the drawparallels and drawmeridians methods.

There are many examples of this in the basemap examples directory.

-Jeff

## ···

On 1/20/11 2:31 PM, R. Mitra wrote:

Hi

I have a set of records with known lat long. I want to show the

concentration of the records with a contour diagram on a world map in

any projection. It cannot spill over to the oceans. I know I have to

use basemap. Is there a quick recipe somewhere I can follow to give

me a desired output. I have gone through earlier posts on this board

but cannot find the right one. Any pointers would be very helpful.

Many thanks.

Best

Mitra

In order to contour, you will need some sort z-value to contour. This

means you need to bin your data. You could use numpy's hist2d, or (I

prefer) matplotlib's hexbin().

I hope that helps!

Ben Root

## ···

On Thursday, January 20, 2011, Jeff Whitaker <jswhit@...146...> wrote:

On 1/20/11 2:31 PM, R. Mitra wrote:

Hi

I have a set of records with known lat long. I want to show the

concentration of the records with a contour diagram on a world map in

any projection. It cannot spill over to the oceans. I know I have to

use basemap. Is there a quick recipe somewhere I can follow to give

me a desired output. I have gone through earlier posts on this board

but cannot find the right one. Any pointers would be very helpful.

Many thanks.

Best

MitraMitra: The basic procedure is this:

1) load you data into 2d numpy arrays (lats, lons, data). lats and lons

must be in degrees (not radians).

2) create a Basemap instance (called "map") for the desired projection.

3) calculate the map projection coordinates of your grid with x,y =

map(lons,lats)

4) contour your data with the contourf method (map.contourf).

5) draw coastlines with the coastlines method.

6) draw lat/lon lines with the drawparallels and drawmeridians methods.There are many examples of this in the basemap examples directory.

-Jeff

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