Hi, I figured out that sometimes it would be useful to have a script for converting a direction map which uses the convention degrees clockwise from North, into the GRASS convention, which is as you well know degrees from East counterclockwise [1]. The aim is to deal with wind direction maps for example, which often use the above mentioned convention [2], but also some other software. I wrote a short tentative of such conversion tool in the form of a grass addon for myself, enclosed. I would like to know:
1) if would be of interest for anyone here, i.e. worth to be published in the addon repo; 2) if you have any idea how to make the several time nested r.mapcalc expression less awful :-) If we call WIND the direction map which uses the convention degrees clockwise from North, and GRASS the output map, the rule that I applied is: IF 0 <= WIND < 270 ; GRASS = 270 - WIND IF WIND = 270 ; GRASS = 360 IF 270 < WIND < 360 ; GRASS 630 - 0 IF WIND = null ; GRASS = 0 NULL otherwise (this latter I have added to check if there is any error. If you are willing to countercheck my assumptions I'd appreciate. cheers, madi [1] http://grass.osgeo.org/grass64/manuals/r.slope.aspect.html [2] http://www.firewords.net/definitions/Wind_direction.htm -- Margherita DI LEO Postdoctoral Researcher European Commission - DG JRC Institute for Environment and Sustainability (IES). Unit H03 – FRC Via Fermi, 2749 I-21027 Ispra (VA) - Italy - TP 261 Tel. +39 0332 78 3600 [email protected] Disclaimer: The views expressed are purely those of the writer and may not in any circumstance be regarded as stating an official position of the European Commission.
r.convert.aspect.py
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