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Vector Data - vmap0

The vmap0 dataset is provided in a very strange file format called "VPF". One of the first tasks is to convert it to a more sensible format which Mapserver will support. I'll cover the details of conversion in a couple of pages time. On this page I'll give a quick introduction to the data in the most general sense and some basic hints and tips for downloading and viewing it.

Downloading vmap0


The first step, obviously, is to download the files. I downloaded them from the US National Geospatial-Intelligence Agency who kindly make them available free of charge. Many other websites allow you to download them for a fee or buy a CD for an inflated price. The files are in tar/gzip compressed format but are still very large; four files are available: North America (246Mb), Europe and North Asia (240Mb), South America and Antarctica (168Mb) and South East Asia, Africa and Australasia (229Mb). These files uncompress to just under 2Gb. I have a reasonable broadband deal, but to save me waiting around I ran a simple bash script to download the files while I watched the TV smilie
#!/bin/bash

BASE=http://geoengine.nima.mil/ftpdir/archive/vpf_data/

for F in v0noa.tar.gz v0eur.tar.gz v0soa.tar.gz v0sas.tar.gz; do
  wget $BASE$F
done

A Guided Tour


The vmap0 data is split into four regions, as mentioned above: North America, Europe and North Asia, South America and Antarctica and SE Asia, Africa and Australasia. We will deal with how these four chunks of data can be combined to create one global dataset on a later page. Each dataset is divided into several directories which contain data like: Boundaries (bnd), elevation (elev), hydrography (hydro), population (pop), transport (trans) and vegitation (veg). These directories contain various files, each of which corresponds to a map layer. Here's a list of the layers I have used in this project - directory/filename first, followed by a description and data type (point, line or area):

  • bnd/polbnda.aft - Political boundaries (area)
  • bnd/polbndl.lft - Political boundaries (line)
  • bnd/coastl.lft - Coastline (line)
  • bnd/oceansea.aft - Ocean/Sea (area)
  • elev/elevp.pft - Spot elevations (point)
  • hydro/watercrsl.lft - Rivers and streams (line)
  • hydro/inwatera.aft - Lakes and inland water (area)
  • pop/builtupa.aft - Built up areas (area)
  • trans/aerofacp.pft - Airports (point)
  • trans/railrdl.lft - Railway tracks (line)
  • trans/roadl.lft - Roads (line)
  • veg/swampa.aft - Swamp, marsh and bog (area)
  • veg/treesa.aft - Trees (area)

Viewing the Layers


The quickest way to view the data is to use ESRI's ArcExplorer application, which can be downloaded here. ArcExplorer runs under Windows and Linux, but I describe the Windows version here.

Install and run ArcExplorer, select Theme -> Add Theme from the main menu and browse into the vmap0 data directory. Browse into the appropriate directory, as shown in figure 1, and select a file.

Selecting a data file to display in ArcExplorer
Figure 1: Selecting a data file to display in ArcExplorer


The data file will then be displayed. Figure 2 shows the European political boundaries. Note that you can change colours and suchlike by right clicking the "theme" in the panel on the left hand side of the map view and altering the properties as you see fit.

ArcExplorer with the European political boundary areas dataset displayed
Figure 2: ArcExplorer with the European political boundary areas dataset displayed


You can add more and more layers this way, which can be useful for getting to grips with the layout of the vmap0 dataset. One word of warning, though, is that if you display many layers at the same time you may find the map draws very slowly. I was forced to copy the vmap0 data files from my file server to the C: drive of my Windows machine to get reasonable performance.

The best way to get to grips with the data is to mess about with ArcExplorer until you know what data files you are interested in. After an introduction to raster datasets on the next page, I'll talk about installing Mapserver and give details of how the vmap0 data files can be converted to a file format that's supported by Mapserver.

A map generated using various vmap0 datasets including roads, trees, railways, international borders, inland water and rivers
Figure 3: A map generated using various vmap0 datasets including roads, trees, railways, international borders, inland water and rivers

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