{"id":228,"date":"2014-01-15T13:31:05","date_gmt":"2014-01-15T13:31:05","guid":{"rendered":"http:\/\/teaching.sociology.ul.ie\/bhalpin\/wordpress\/?p=228"},"modified":"2014-04-19T14:46:24","modified_gmt":"2014-04-19T14:46:24","slug":"mapping-with-python-and-stata","status":"publish","type":"post","link":"https:\/\/teaching.sociology.ul.ie\/bhalpin\/wordpress\/?p=228","title":{"rendered":"Mapping with Python and Stata"},"content":{"rendered":"

Elevation data for large swathes of the planet have been collected by NASA and are available to download from http:\/\/dds.cr.usgs.gov\/srtm\/<\/a>.<\/p>\n

The data is contained in binary files, each representing a 1-degree by 1-degree “square”. Here are five lines of Python and four lines of Stata that will turn the data into a simple graph:<\/p>\n

import struct
\nfile = open(\"data\/N52W011.hgt\", \"r\")
\nfor y in range(1201):
\nfor x in range(1201):
\nprint y, x, struct.unpack(\">h\",file.read(2))[0]<\/code><\/p>\n

Do python file.py > map.dat<\/code>. Then run this Stata code:<\/p>\n

infile i j height using \/tmp\/ext.dat
\ngen h2 = int(sqrt(height))
\nreplace h2 = 30 if h2<=0
\nhmap j i h2, nosc<\/code><\/p>\n

\"Low<\/p>\n

(Hi-res version<\/a>.)<\/p>\n

You may need to install Python’s struct<\/code> package, and Stata’s hmap<\/code> add on, but they’re available from the usual locations.<\/p>\n

There are better ways of doing this, of course: it’s slow, the aspect ratio is wrong, the colours are not ideal and the axis labelling is bad. Even worse, it is a complete abuse of the hmap<\/code> add-on. It’s a quick and dirty way to turn binary data into pictures, all the same.<\/p>\n","protected":false},"excerpt":{"rendered":"

Elevation data for large swathes of the planet have been collected by NASA and are available to download from http:\/\/dds.cr.usgs.gov\/srtm\/. The data is contained in binary files, each representing a 1-degree by 1-degree “square”. Here are five lines of Python and four lines of Stata that will turn the data into a simple graph: import … Continue reading Mapping with Python and Stata<\/span> →<\/span><\/a><\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"image","meta":{"footnotes":""},"categories":[6,4],"tags":[],"_links":{"self":[{"href":"https:\/\/teaching.sociology.ul.ie\/bhalpin\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/228"}],"collection":[{"href":"https:\/\/teaching.sociology.ul.ie\/bhalpin\/wordpress\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/teaching.sociology.ul.ie\/bhalpin\/wordpress\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/teaching.sociology.ul.ie\/bhalpin\/wordpress\/index.php?rest_route=\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/teaching.sociology.ul.ie\/bhalpin\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=228"}],"version-history":[{"count":14,"href":"https:\/\/teaching.sociology.ul.ie\/bhalpin\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/228\/revisions"}],"predecessor-version":[{"id":249,"href":"https:\/\/teaching.sociology.ul.ie\/bhalpin\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/228\/revisions\/249"}],"wp:attachment":[{"href":"https:\/\/teaching.sociology.ul.ie\/bhalpin\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=228"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/teaching.sociology.ul.ie\/bhalpin\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=228"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/teaching.sociology.ul.ie\/bhalpin\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=228"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}