Country Data Processing

2013-02-01T09:33:55Z

⚠️JohnCox: /* GRASS Installation */

This tutorial describes how to
* find free data of country on Internet
* create new GRASS location
* import found data into GRASS
* create new vector layers from existing data
* create labels
* display map of a country

= GRASS Installation =
Required elements
* GRASS GIS 6.2.2 system installed
* download SPEARFISH data http://grass.itc.it/sampledata/spearfish_grass60data-0.3.tar.gz

Create directory structure required for this tutorial
* dataset directory
$ mkdir ~/grass
* input data directory
$ mkdir ~/grass/indata

Create GRASS location using SPEARFISH data to be able create new locations

$ cd ~/grass
$ tar zxf spearfish_grass60data-0.3.tar.gz

Start GRASS

$ grass -text spearfish60/PERMANENT
$ [http://lux-essay.com/ essay]

= Obtaining Data =

We assume that one wants to create UK map. Following steps can be easily
applied to other countries' data.

Country related GIS data can be obtained from
[http://www.maproom.psu.edu/dcw/ Digital Chart of the World].

First create country related input directory

$ mkdir ~/grass/indata/uk

Let's download UK data
* go to [http://www.maproom.psu.edu/dcw/ Digital Chart of the World]
* click Europe link
* choose United Kingdom in select box on the right and click Continue
* page _Digital Chart of the World Layer Interface for United Kingdom_ will be displayed
* click Download Data button
* another page will be shown, mark checkboxes
** Populated Places (Polygon)
** Roads (Line)
** Rail Roads (Line)
* click Continue
* on new page click Compute Data
* on new page you will be able to obtain set of data (<NUMBER> is part of filename with data exported by DCW)
<NUMBER>.tar.Z
* do not hesistate to download data into ~/grass/indata/uk directory

== Downloading Names of Cities ==
[http://earth-info.nga.mil/gns/html/ NGA GEOnet Names Server] provides free GIS data
containing positions of cities and their names.

Data can be downloaded from FTP server

ftp://ftp.nga.mil/pub/gns_data/

Direct link to UK GNS data

ftp://ftp.nga.mil/pub/gns_data/uk.zip

Download UK data into ~/grass/indata/uk directory.

= Importing Data =
Importing data into GRASS is two fold step
* create new location with one piece of data
* import remaining data

== Creating New Location ==
One can create new location using another location. We will use SPEARFISH location
to create UK location.

Start GRASS

$ cd ~/grass
$ grass62 -text spearfish60/PERMANENT (you need grass 6.2.x for this to work)

Enter UK input data directory and unpack downloaded data from DCW

$ cd indata/uk
$ tar zxf <NUMBER>.tar.Z

You will have several files
;ponet.e00: country borders
;pppoly.e00: populated places
;rdline.e00: road network
;rrline.e00: rail road network

We will create UK GRASS location using country borders. In SPEARFISH GRASS session
use following commands to create location uk and layer borders

$ cd ~/grass
$ v.in.ogr dsn=indata/uk/ponet.e00 layer=ARC output=borders location=uk

New location is created. Exit SPEARFISH GRASS session and start GRASS UK session

$ cd ~/grass
$ grass62 -text uk/PERMANENT

You can display UK borders

$ g.region vect=borders # set region to display
$ d.mon x0 # create GRASS monitor
$ d.vect map=borders # display borders

== Importing Rest of the Data ==

Having GRASS UK location we can import rest of the data (population places,
road and rail networks)

$ cd ~/grass
$ grass -text uk/PERMANENT
$ v.in.ogr dsn=indata/uk/pppoly.e00 layer=ARC output=pcities
$ v.in.ogr dsn=indata/uk/rdline.e00 layer=ARC output=roads
$ v.in.ogr dsn=indata/uk/rrline.e00 layer=ARC output=rails

Display data

$ d.mon x0
$ g.region vect=borders
$ d.vect map=borders color=black width=1.2
$ d.vect map=roads color=grey
$ d.vect map=pcities color=brown

or save it to PNG file uk.png

$ GRASS_WIDTH=1024 GRASS_HEIGHT=1024 GRASS_PNGFILE=uk.png d.mon start=PNG
$ d.mon select=PNG
$ d.vect map=borders color=black width=1.2
$ d.vect map=roads color=grey
$ d.vect map=pcities color=brown
$ d.mon stop=PNG

== Import Data from GNS ==
Downloaded GNS data can be imported into GRASS using v.in.gns script.

Uncompress GNS data

$ cd ~/grass/indata/uk
$ unzip uk.zip

Start GRASS UK session

$ cd ~/grass
$ grass62 -text uk/PERMANENT

Import data

$ v.in.gns file=indata/uk/uk.txt vect=cities

= Processing Data =
GNS data contains information about large amount of cities. Usually it is
uncovinient to see all this data on a map. GRASS allows us to create new
vector layers of cities.

Example below will show how to create new vector layer from GNS data for major
country cities.

Start GRASS session
$ cd ~/grass
$ grass62 -text uk/PERMANENT

Extract data from cities vector layer to mcities vector layer

$ v.extract --o output=mcities input=cities where="(DSG='PPLA' or DSG='PPLC') and NT='N'"

Above selects those names of cities, which
* name type is 'N'
* Feature Designation Code (DSG) is PPLA or PPLC

Create labels using FULLNAME column

$ v.label labels=mcities map=mcities column=FULLNAME size=0.1

Display map

$ d.mon x0
$ d.vect map=borders color=black width=1.2
$ d.vect map=mcities icon=basic/circle color=black fcolor=red size=4
$ d.labels labels=mcities

Other columns can be used to filter data or create labels. GNS columns are described at
[http://earth-info.nga.mil/gns/html/help.htm GNS Help page].

[[Category: Documentation]]

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Country Data Processing