Resolution of satellite imagery

srikanthkpsrikanthkp Global Mapper UserPosts: 23Trusted User
edited June 2015 in Technical Support
Hello,
I have a satellite imagery. The vendor says this is 50 cm resolution. Can I verify this using GM ?

Thanks
Srikanth

Comments

  • bmg_bobbmg_bob Global Mapper Programmer Posts: 2,038
    edited June 2015
    Hello Srikanth,

    Load the data set into Global Mapper, open the Control Center, and click the Metadata... button. The resulting metadata display includes the resolution.

    Cheers,

    Bob
  • srikanthkpsrikanthkp Global Mapper User Posts: 23Trusted User
    edited June 2015
    Dear Bob,
    I am using GM v16.0. I am not seeing resolution row in meta data display. It has the following rows :


    FILENAME=D:\kps\ADA\CAEImagery\HAL-Imagery\HAL_2009-2013_50cm_Colr_C3R3.tif
    DESCRIPTION=<HAL_2009-2013_50cm_Colr_C3R3.tif> Contents Not Specified | Contents Not Specified | Contents Not Specified
    UPPER LEFT X=77.5617883333
    UPPER LEFT Y=13.0372275000
    LOWER RIGHT X=77.6147304167
    LOWER RIGHT Y=12.9781116667
    WEST LONGITUDE=77.56178833° E
    NORTH LATITUDE=13.03722750° N
    EAST LONGITUDE=77.61473042° E
    SOUTH LATITUDE=12.97811167° N
    UL CORNER LONGITUDE=77.56178833° E
    UL CORNER LATITUDE=13.03722750° N
    UR CORNER LONGITUDE=77.61473042° E
    UR CORNER LATITUDE=13.03722750° N
    LR CORNER LONGITUDE=77.61473042° E
    LR CORNER LATITUDE=12.97811167° N
    LL CORNER LONGITUDE=77.56178833° E
    LL CORNER LATITUDE=12.97811167° N
    PROJ_DESC=Geographic (Latitude/Longitude) / WGS84 / arc degrees
    PROJ_DATUM=WGS84
    PROJ_UNITS=arc degrees
    EPSG_CODE=EPSG:4326
    COVERED AREA=37.782 sq km
    NUM COLUMNS=11551
    NUM ROWS=12898
    NUM BANDS=3
    COLOR BANDS=0,1,2
    PIXEL WIDTH=0.0000046 arc degrees
    PIXEL HEIGHT=0.0000046 arc degrees
    BIT DEPTH=24
    SAMPLE TYPE=Unsigned 8-bit Integer
    TIFF_DESC=Contents Not Specified | Contents Not Specified | Contents Not Specified
    PHOTOMETRIC=RGB Full-Color
    BIT_DEPTH=24
    SAMPLE_FORMAT=Unknown Format (0)
    ROWS_PER_STRIP=1
    COMPRESSION=None
    PIXEL_SCALE=( 0.00000458333333, 0.00000458333333, 1 )
    TIEPOINTS=( 0.00, 0.00, 0.00 ) --> ( 77.5617883333, 13.0372275000, 0.0000000000 )
    MODEL_TYPE=Geographic lat-long system
    RASTER_TYPE=Pixel is Area


    How to resolve the problem ?

    Thanks
    Srikanth
  • bmg_bobbmg_bob Global Mapper Programmer Posts: 2,038
    edited June 2015
    Hello Srikanth,

    PIXEL_WIDTH and PIXEL_HEIGHT contain the resolution, though it appears that the data is in a geodetic coordinate system, so the unit is degrees rather than meters. Using our Geographic Calculator program, I was able to determine that at the central latitude (roughly 13 degrees north), 0.0000046 arc degrees represents 50 cm. Based on this calculation, it appears that your data does have 50 cm resolution.

    Cheers,

    Bob
  • Ice Age MarkIce Age Mark Global Mapper User Posts: 300Trusted User
    edited June 2015
    Srikanth,


    When the resolution (pixel size) is in degrees, or some other inconvenient or unfamiliar unit, you can pretend you are going to export as a Geotiff, then click on "Click here to calculate spacing in other units"; use that for a converter, and then just cancel out of that dialog and the export. (You can only do it once without closing and then re-opening that feature.)


    Regards,


    Mark
  • srikanthkpsrikanthkp Global Mapper User Posts: 23Trusted User
    edited June 2015
    Thanks for the reply. It matches the calculations that
    0.00000458333333 * 3600 * 30 = 0.494964 m or ~ 50 cm


    Regards
    Srikanth
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