[talk-ph] Notes on using GADM or PhilGIS boundary data

Eugene Alvin Villar seav80 at gmail.com
Fri May 20 06:41:32 BST 2011

Hello guys,

Some of you may already know that there is a globally available data
for administrative boundaries from country level down to the
sub-municipality level (depending on country). This is the Global
Administrative Areas (GADM) dataset <http://gadm.org/>. They have data
for the Philippines down to the barangay level. If you need a freely
available data like that then you can use GADM.

The GADM data for the Philippines is in one big chunk. If you need
smaller sets (e.g., just for Metro Manila or just for a single
province), you can check out PhilGIS <http://www.philgis.org/> which
has taken the GADM data, added PSGC metadata, and provided downloads
on a per-province level. (BTW, PhilGIS contains other freely-available
datasets aside from boundaries.)

However take note of the restrictions and limitations:

1. License. The GADM data "is freely available for academic and other
non-commercial use. Redistribution, or commercial use, is not allowed
without prior permission." Same with PhilGIS: "For academic,
non-profit, and non-commercial use only." This means that we *cannot*
add GADM data into OSM, which allows redistribution and commercial use
even without prior permission.

2. The data has quality issues.

2.1. Inaccurate positioning: Despite saying that the data is in WGS84
datum (which GPS devices use), they don't actually match what's on the
ground. For example, here are two comparisons between the GADM data
and the data in OSM:

a. central Quezon City:

b. Northern Caloocan:

2.2. Outdated data: The dataset is missing new barangays,
municipalities, and cities. And the embedded data sometimes contain
old names.

If these restrictions and limitations are not a problem for you, then
you should use them in your mapping applications, especially if the
current OSM data is incomplete or inadequate for your needs.


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