I've got some data from "http://srtm.csi.cgiar.org/SELECTION/inputCoord.asp" and it is in *.asc form. To process them I need to convert them to shapefile (need to merge them all into one shapefile and add attribute table, on and on …), but I don't know how. Some web sites such as "http://converter.mygeodata.eu/ " do convert my data but I'm talking about 2.5 GB of data and it is impossible for me to upload this much data … how can I convert them inside QGIS or ArcGIS ??? Is there another software that can convert my *.asc file into *.shp ???
A lot of thanks
Best Answer
You can try the GDAL utility gdal_polygonize.py. For example, to create a shapefile output.shp from input.asc:
If there is no spatial data associated with it, you'll need to have some kind of geographical data to 'bind' it to. The LSOA data column, in some of that data, links it to an object in the local authority, which suggests to me you'll struggle to do this, without the 'linked' spatial data inferred.
The data you need is LSOA data:
Lower Layer Super Output Area - (LSOA)
These have a minimum population of 1,000, with an overall mean of 1,500. They are built from groups of Output Areas. There are around 34,000 LSOAs in England and Wales.
I'd go back to that site and try and get hold if it, as once you have this LSOA data, you cna bind your statistical data to it.
There are four geographies that will be discussed in this study. The bottom three are part of the statistical hierarchy:
Local Authority - LA,
Middle Layer Super Output Area - MSOA,
Lower Layer Super Output Area - LSOA,
Output Area - OA.
Local authority - LA
Local authority is a generic term for any level of local government in the UK. LAs include non-metropolitan districts, metropolitan districts, unitary authorities and London boroughs (in England); Welsh unitary authorities; Scottish council areas; and Northern Irish district council areas.
Middle Layer Super Output Area - (MSOA)
These areas have a minimum population of 5,000, with an overall mean of 7,200. They were built from groups of Lower Layer Super Output Areas and constrained by the local authority boundaries of 2003. There are around 7,000 MSOAs in England and Wales.
Lower Layer Super Output Area - (LSOA)
These have a minimum population of 1,000, with an overall mean of 1,500. They are built from groups of Output Areas. There are around 34,000 LSOAs in England and Wales.
Output Area - (OA)
In England and Wales OAs were designed from the 2001 Census. Postcodes were grouped into OAs according to a set of design criteria. OAs have a minimum population size of 100 with an overall mean of 300. There are around 175,000 OAs in England and Wales.
Best Answer
You can try the GDAL utility gdal_polygonize.py. For example, to create a shapefile output.shp from input.asc:
Prerequisites: GDAL, Python and GDAL Python bindings.
But... Are you sure that SHP is the right format in order to work with such huge data?