[GRASS-user] i.image.mosaic generates blank mosaic

GRASS GRASS user
1

Hello all,

I've been trying to use the i.image.mosaic command in GRASS 6.4.1 in Ubuntu
to stitch two raster image files (technically I'm trying to stitch only the
blue channel of an RGB truecolor image) but I'm just getting a blank image
file as the output.

I set the region to the proper region and it's not a "NULL" file, but
rather, it just doesn't show up. If I use the r.patch command they both
patch into one single raster, but unfortunately the colors aren't really
balanced.

Does anyone know what's up? Here's the output from r.info on the mosaicked
image using i.image.mosaic:

(Tue Nov 12 17:52:43 2013)

r.info
map=Warehouse17.blue.georectified.Warehouse18.blue.georectified.mosaic@Warehouse_Mosaic

+----------------------------------------------------------------------------+

| Layer: Warehouse17.blue.georectified Date: Tue Nov 12 16:57:08 2013
|

| Mapset: Warehouse_Mosaic Login of Creator: user
|

| Location: Parking_Lot_Test_4_UTM
|

| DataBase: /home/user/Documents/grassdata
|

| Title: ( Warehouse17.blue.georectified.Warehouse18.blue.georectified.m
|

| Timestamp: none
|

|----------------------------------------------------------------------------|

|
|

| Type of Map: raster Number of Categories: 511
|

| Data Type: CELL
|

| Rows: 5232
|

| Columns: 5487
|

| Total Cells: 28707984
|

| Projection: UTM (zone 17)
|

| N: 3280373.34673833 S: 3280265.18938071 Res: 0.02067228
|

| E: 372335.90758975 W: 372236.78889019 Res: 0.01806428
|

| Range of data: min = 0 max = 511
|

|
|

| Data Description:
|

| generated by r.mapcalc
|

|
|

| Comments:
|

| if(isnull(Warehouse17.blue.georectified),
|

| Warehouse18.blue.georectified + 256, Warehouse17.blue.georectified)
|

| i.image.mosaic "image1=Warehouse17.blue.georectified" "image2=Warehouse
|

| 18.blue.georectified"
|

|
|

+----------------------------------------------------------------------------+

(Tue Nov 12 17:52:43 2013) Command finished (0 sec)

Thanks, and let me know what you guys think.

Moses

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2

nyflyer wrote:

I’ve been trying to use the i.image.mosaic command in GRASS 6.4.1 in Ubuntu

to stitch two raster image files (technically I’m trying to stitch only the

blue channel of an RGB truecolor image) but I’m just getting a blank image

file as the output.

Try to re-assign a color table, e.g.:

r.colors Mosaic color=grey -e

and see if that works out.

Nikos

–%<—

| Total Cells: 28707984

| Projection: UTM (zone 17)

| N: 3280373.34673833 S: 3280265.18938071 Res: 0.02067228

| E: 372335.90758975 W: 372236.78889019 Res: 0.01806428

| Range of data: min = 0 max = 511

—>%–

Wow, looks pretty huge!

3

On Fri, Nov 15, 2013 at 4:12 PM, Nikos Alexandris
<nik@nikosalexandris.net> wrote:

nyflyer wrote:

I've been trying to use the i.image.mosaic command in GRASS 6.4.1 in
Ubuntu

Please note that 6.4.1 isn't particularly new.

http://trac.osgeo.org/grass/wiki/Release/6.4.2-News
"Between 6.4.1 and the current 6.4.2 more than 770 updates have been applied."

http://trac.osgeo.org/grass/wiki/Release/6.4.3-News
"Over 830 new features and bug-fixes have been applied since 6.4.2. "

(and it is time to get 6.4.4 out...)

to stitch two raster image files (technically I'm trying to stitch only
the blue channel of an RGB truecolor image) but I'm just getting a blank image
file as the output.

You have the computational region right?
...

--%<---

| Total Cells: 28707984
| Projection: UTM (zone 17)
| N: 3280373.34673833 S: 3280265.18938071 Res: 0.02067228
| E: 372335.90758975 W: 372236.78889019 Res: 0.01806428

A remark: The current resolution is hence 1-2cm given that you are in UTM?

BTW: You may consider to check if you do not want to have square
pixels (and if so, why they aren't).

Markus

4

While we discuss it, another good step you want to apply before doing
the actuall stitch is to trim the rasters' area by a couple of pixels
before hand. Usually the borders is full with pesky pixel with
distorsions/noise, which might contaminate your mosaic.

N

On Fri, Nov 15, 2013 at 10:28 PM, Markus Neteler <neteler@osgeo.org> wrote:

On Fri, Nov 15, 2013 at 4:12 PM, Nikos Alexandris
<nik@nikosalexandris.net> wrote:

nyflyer wrote:

I've been trying to use the i.image.mosaic command in GRASS 6.4.1 in
Ubuntu

Please note that 6.4.1 isn't particularly new.

http://trac.osgeo.org/grass/wiki/Release/6.4.2-News
"Between 6.4.1 and the current 6.4.2 more than 770 updates have been applied."

http://trac.osgeo.org/grass/wiki/Release/6.4.3-News
"Over 830 new features and bug-fixes have been applied since 6.4.2. "

(and it is time to get 6.4.4 out...)

to stitch two raster image files (technically I'm trying to stitch only
the blue channel of an RGB truecolor image) but I'm just getting a blank image
file as the output.

You have the computational region right?
...

--%<---

| Total Cells: 28707984
| Projection: UTM (zone 17)
| N: 3280373.34673833 S: 3280265.18938071 Res: 0.02067228
| E: 372335.90758975 W: 372236.78889019 Res: 0.01806428

A remark: The current resolution is hence 1-2cm given that you are in UTM?

BTW: You may consider to check if you do not want to have square
pixels (and if so, why they aren't).

Markus
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5

Thank you so much for your responses...they were very helpful.

Modifying the color table seems to have gotten it working right. Yes, you're
right, I probably need to upgrade my version of GRASS. Thanks once again for
your help everyone.

Respectfully,

Moses

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