[GRASSLIST:9069] Re: GRASS 6 in a nutshell tutorial

[Ian MacMillan]

Luigi, if you look at r.info and v.info, you will only find the  
projection information of your location, not necessarily the  
projection/datum/etc. information of the original data (I believe).  Do  
you have the original metadata?  If not, try running gdalinfo on your  
original data files to determine their original projection info.

man gdalinfo
will give you the correct syntax.

G'luck
Ian

On Nov 14, 2005, at 2:06 PM, Luigi Ponti wrote:

> Thanks Amish,
>
> looking at v.info and r.info, it seems the two maps have the same  
> projection (see below). However, when looking at the output "d.where  
> -w" for a sample map point (the San Francisco Bay), the longitude is  
> very different in the two maps:
>
>                                                   WGS84 Co-ordinates
>             EAST:             NORTH:               LON:
>             -191114.6346037    -24240.66895625  143:03:58.588289W    
> 29:24:27.1
> (San Francisco Bay on the California State vector layer - WRONG)
>
>  1839139.30311877    663981.00484798  122:19:50.783112W   37:57:48.1
> (San Francisco Bay on the Elevation Model raster layer - CORRECT)
>
> Do you think this could be due to an error in the import process or  
> should I just look for another vector map?
>
> Thanks again,
>
> Luigi
>
>
>
> v.info map=state layer=1
> +---------------------------------------------------------------------- 
> ------+
> | Layer:    state                          Organization:                
>       |
> | Mapset:   luigi                          Source Date:                 
>       |
> | Location: Cal_nad83-zone3                Name of creator:             
>       |
> | Database: /home/andy                                                  
>       |
> | Title:                                                                
>       |
> | Map Scale:  1:1                                                       
>       |
> | Map format: native                                                    
>       |
> |---------------------------------------------------------------------- 
> ------|
> |   Type of Map:  Vector (level: 2)                                     
>       |
> |                                                                       
>       |
> |   Number of points:       0               Number of areas:      51    
>       |
> |   Number of lines:        0               Number of islands:    48    
>       |
> |   Number of boundaries:   59              Number of faces:      0     
>       |
> |   Number of centroids:    51              Number of kernels:    0     
>       |
> |                                                                       
>       |
> |   Map is 3D:              0                                           
>       |
> |   Number of dblinks:      1                                           
>       |
> |                                                                       
>       |
> |   Projection: Lambert Conformal Conic (zone 0)                        
>       |
> |            N: 922206.900    S: -701781.905                            
>       |
> |            E: 1043412.917     W: -374425.808                          
>       |
> |            B: 0.000         T: 0.000                                  
>       |
> |                                                                       
>       |
> |   Digitize threshold: 0.00000                                         
>       |
> |   Comments:                                                           
>       |
> |                                                                       
>       |
> +---------------------------------------------------------------------- 
> ------+
>
>
> r.info map=e10g at PERMANENT
> +---------------------------------------------------------------------- 
> ------+
> | Layer:    e10g                           Date: Tue Nov  8 17:25:24  
> 2005    |
> | Mapset:   PERMANENT                      Login of Creator: andy       
>       |
> | Location: Cal_nad83-zone3                                             
>       |
> | DataBase: /home/andy                                                  
>       |
> | Title:     ( e10g )                                                   
>       |
> |---------------------------------------------------------------------- 
> ------|
> |                                                                       
>       |
> |   Type of Map:  raster              Number of Categories: 5443        
>       |
> |   Data Type:    CELL                                                  
>       |
> |   Rows:         7192                                                  
>       |
> |   Columns:      11628                                                 
>       |
> |   Total Cells:  83628576                                              
>       |
> |        Projection: Lambert Conformal Conic (zone 0)                   
>       |
> |            N:    3353466    S:   -3838238   Res: 999.95884316         
>       |
> |            E:    6073284    W:   -5555183   Res: 1000.04016168        
>       |
> |   Range of data:    min =  -84 max = 5443                             
>       |
> |                                                                       
>       |
> |   Data Source:                                                        
>       |
> |                                                                       
>       |
> |                                                                       
>       |
> |                                                                       
>       |
> |   Data Description:                                                   
>       |
> |    generated by r.proj                                                
>       |
> |                                                                       
>       |
> |                                                                       
>       |
> +---------------------------------------------------------------------- 
> ------+
>
> Hamish wrote:
>
>>> I have imported both the vector and the raster with minimum trouble,  
>>> since the first has a .prj file which GRASS recognized, and the  
>>> second
>>>
>>> had a detailed import tutorial in the cygwin-GRASS install page.  
>>> However, despite the fact the the two layers supposedly have the  
>>> same NAD83 projection info (I did not enter anything manually), when  
>>> I try
>>> to  display them together on a GRASS monitor, the state layout is in
>>> the  middle of the ocean compared to the elevation raster.
>>>
>>> Is there a way to overlap the two layers or to chek for a coordinate
>>> error?
>>>
>>
>>
>> r.info and v.info will give you the map extents, you should then be  
>> able
>> to figure out which is correct.
>>
>> Also try "d.where -w" to give you a lat/lon value for different parts  
>> of your map which you can compare to the map on the wall.
>>
>>
>> Hamish
>>
>>
>>
>
>
 >
 >
What happens if a big asteroid hits Earth? Judging from realistic  
simulations involving a sledge hammer and a common laboratory frog, we  
can assume it will be pretty bad.
  - Dave Barry


-------------------------------------------------------------
This message has been scanned by Postini anti-virus software.