[GRASS-dev] MODIS import in GRASS6.4

[Hamish]

Franz wrote: 
> I have been using MODIS datasets in MRT tool and MATLAB but Now I
> want to import MODIS projected datasets to GRASS .
> 
> At http://grass.osgeo.org/wiki/MODIS
> is described methods to do this.


Markus answered most of these, but I'll throw in another 2c.

 
>  Question 1: can those methods be applied using a GRASS Script?
> (I believe so)

(yes)

> Question 2: in method 1 (http://grass.osgeo.org/wiki/MODIS#Method_1),
> It’s said to create a Project/mapset with EPSG 3266. Why that system?
> And Why if gdal_translate will create geotiff in EPSG4326?

It says you might try that, not that you definitely should.
EPSG:32662 is "Plate Carree"

# WGS 84 / Plate Carree
<32662> +proj=eqc +lat_ts=0 +lon_0=0 +x_0=0 +y_0=0 +ellps=WGS84 +datum=WGS84 +units=m +no_
defs  <>

A number of global datasets ship in this. With ~4km pixels a possible
datum error of 150m away from the wgs84 DATUM isn't going to be very
noticeable. but a switch between the wgs84 ELLIPSOID and a perfect
sphere can lead to errors of ~25km.

Consult your metadata. Hopefully it gives some guidance (often it
doesn't though, hence the confusion).

 
> Question 3:
> Regarding a_ullr. This flag asks for Upperleft and lowerright. This
> means that those values are the same for all files. But in the case
> that they may vary. How can I obtain them from MODIS Metadata/header?
> And this would mean that the we are dealing with a regular dataset
> because in a Geostationary dataset this wouldn’t be possible (I guess).

parse gdalinfo or as Markus suggested the associated XML file?)


> Question 4:
> What is the –co flag? I read Gdal_translate description
> but I didn’t find it very clear..

see the r.out.gdal help page for more on compression.


> Question 7: if we define
> a_ullr, this means that GCP points are
> not being used right?

if gdalinfo can see GCPs but not map bounds, use 'gdalwarp -tps' to
apply the GCPs and make a georeferenced image which can be loaded into
grass.


> Regarding method 2, that
> is based on GRASS6.5, will this be
> implemented for grass 6.4? (the –i
> flag)

if no problems are reported in testing it will be backported to 6.4.1.


Hamish