[GRASS-user] r.to.vect to selected locations only

maning sambale emmanuel.sambale at gmail.com
Sun Jun 22 23:46:25 EDT 2008


Here's the process I plan to do for my image classification

1. Create an unsupervised classification from TCAP images to get
clusters of pure pixel values.
2. Convert to vector.
3. Create a random location of vector points.
4. From the converted vector layer, select random polygons
(approximately 60 polys for each class).
5. Label training polygons for the desired classification classes
6. Run smap classification

I will be running this method for a series of LANDSAT images (one tile
at a time).

My problem is by converting the whole image from raster to vector
areas, the v.to.rast module reports "Killed" and could not complete
the conversion.
This maybe due to the whole image being large.

 Type of Map:  raster               Number of Categories: 47              |
 |   Data Type:    CELL                                                       |
 |   Rows:         7518                                                       |
 |   Columns:      8504                                                       |
 |   Total Cells:  63933072                                                   |
 |        Projection: UTM (zone 51)                                           |
 |            N:     746814    S:     532551   Res:  28.5                     |
 |            E:     857451    W:     615087   Res:  28.5                     |
 |   Range of data:    min = 1  max = 47

I've tried r.neighbors to reduce number of areas with less than 1-10
pixels, but this process outputs vectors layers with mixed pixel
values, thus making it difficult to use in MLC or SMAP as training

What I need is to, limit raster to vector conversion to the desired
randomly selected locations only. So that r.to.vect could complete the

Any ideas?


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