Opened 5 years ago

Last modified 10 months ago

#2564 new enhancement

r.what: remove 400 maps limit and add some new output options

Reported by: sbl Owned by: grass-dev@…
Priority: normal Milestone: 7.6.2
Component: Raster Version: svn-trunk
Keywords: r.what Cc:
CPU: Unspecified Platform: Unspecified

Description

r.what is currently the most efficient tool for sampling (single) STRDS at point locations. Usage of r.what for space time data sets however is hampered by the current limit of 400 maps. Would be nice if that limit could be overcome. Memory may be an issue in case of thousands of maps?

See discussion on the mailinglist: http://thread.gmane.org/gmane.comp.gis.grass.devel/62452/focus=62472

In that context also an option/flag to choose between vertical and horizontal output would be useful (columns for thousands of maps will probably trouble spread sheet software).

Finally, when using a vector map as input it would be nice if the category (or content from another column) could be written into the "site name" column of the output, so a resulting table can be linked more easily to the original data.

Change History (12)

comment:1 Changed 5 years ago by huhabla

I have just committed a new temporal module called t.rast.what in trunk (r64349 - r64351) that utilized r.what to sample space time raster datasets using vector points. It provides three output layouts that transforms the r.what output into row or column layouts. It can run several r.what processes in parallel using a maximum of 400 raster map layer in a single r.what process.

Please have a look at it.

Any feedback about its performance, usefulness and handling is highly welcome.

Improving r.what to allow more than 400 maps is simple, just edit the fixed value in the source. But, editing this value may cause open file handler limit problems with your OS. However, these limits can be adjusted at kernel level configuration for Linux.

Implementing a more intelligent file handling solution requires more effort.

comment:2 Changed 4 years ago by neteler

See also #32

comment:3 Changed 4 years ago by huhabla

I would like to see a PyGRASS implementation of r.what that is easier to maintain. Especially the database handling in PyGRASS is much, much easier than in C. However, PyGRASS supports only sqlite and postgresql as backends, since it fully ignores the GRASS database library and uses Python bindings.

I have implemented a simple prototype to sample a space time raster dataset with vector points, that allows to have a vector attribute table column as identifier of the points in the output. It is slower than t.rast.what but a good example of what can be done using PyGRASS and the temporal framework.

https://bitbucket.org/huhabla/temporal-raster-sampling/overview

comment:4 Changed 4 years ago by neteler

Milestone: 7.1.07.2.0

Milestone renamed

comment:5 Changed 3 years ago by neteler

Milestone: 7.2.07.2.1

Ticket retargeted after milestone closed

comment:6 Changed 3 years ago by martinl

Milestone: 7.2.17.2.2

comment:7 Changed 2 years ago by martinl

Milestone: 7.2.27.4.0

All enhancement tickets should be assigned to 7.4 milestone.

comment:8 Changed 2 years ago by neteler

Milestone: 7.4.07.4.1

Ticket retargeted after milestone closed

comment:9 Changed 20 months ago by neteler

Milestone: 7.4.17.4.2

comment:10 Changed 16 months ago by martinl

Milestone: 7.4.27.6.0

All enhancement tickets should be assigned to 7.6 milestone.

comment:11 Changed 12 months ago by martinl

Milestone: 7.6.07.6.1

Ticket retargeted after milestone closed

comment:12 Changed 10 months ago by martinl

Milestone: 7.6.17.6.2

Ticket retargeted after milestone closed

Note: See TracTickets for help on using tickets.