GEOTIFF IMPORTATION

IMPORTANT: Images with system correction in the GeoTIFF format 

Almost every satellite image presently distributed by private companies or research organizations are geometrically corrected through a mathematical model the uses data that is transmitted together with the image data. Thus, ephemeris data (satellite position and velocity), attitude data as well as some parameters that are inherent to the operation of the instrument (sensor) are used to define the geographic coordinates associated to the moment of acquisition of a certain pixel of the image. Since these data transmitted by the satellite may contain errors, the resultant system corrected image (called that way because it uses information of the system "satellite+instrument") may also contain errors. The most common is the positioning error caused by the errors in the position of the satellite. This error makes the image as a whole be shifted in respect to its correct position.

Due to that it is important to have in mind that an image in the GeoTIFF format could not be completely georeferenced Frequently, the GeoTIFF images have only the system geometric correction and need to be further refined with ground control points. In SPRING this refinement process can only be made through the REGISTRATION module, this module requires that the image be previously converted to the GRIB format with IMPIMA.

Following we present the definitions of the TIFF and GeoTIFF formats, so that the user can used them properly.

Description of the TIFF format:

  1. Can support images with 1, 2, 4, 8, 16 e 32 bits per pixel;
  2. The types of data format are positive integers, integers (positive ad negative), and IEEE (32 bits);
  3. From 1 to n bands.

Description of the GEOTIFF format:

  1. Adds new labels (tags) to the TIFF;
  2. Provides tags for geocoding and georeferencing:
    1. Geocoding: a method to position the image on the surface of the Earth (pixel --> X,Y), through ground control points that can be described in plane or geographic coordinates;
    2. Georeferencing: projection and datum information;
    3. If the geocoding tags exist, the Georeferencing tags are not mandatory;
    4. We can geocode a TIFF image using an auxiliary file with the .tfw extension.

Description of the GEOTIFF format for SPRING:

  1. Images with less than 8 bits/pixel will be converted to 8 bits/pixel;
  2. We can convert images with more than 8 bits/pixel to 8 bits/pixel using the following algorithms:
    1. Linear : converts the data starting from the minimum up to the maximum value of the pixel;
    2. Statistics : enhances the pixels in the range of n standard deviations around the mean of the image;
    3. 2% : enhances the image starting from 2% of the beginning up to 2% of the end of the histogram;
  3. For images with more than 8 bits:
    1. Present the minimum and maximum values of the histogram and the button to draw the histogram, allowing the user to change these values;
    2. Activates the code for the conversion to 8 bits.
  4. The TIFF/GEOTIFF image can be imported into SPRING for the following data types:
    1. Image;
    2. Classified Image;
    3. Synthetic Image;
    4. Labeled Image;
    5. Grid.

Description of the Import Interface

Following we present the sequence of dialog boxes of the importation interface.








Configure your Chart

Problems with the importation of GeoTIFF

Remember to always use the "properties" button to check the data relative to the GeoTIFF file

  • Situations where the DATUM defined in the GeoTIFF file does not make part of the list of Earth  Models of SPRING:

Cancel the execution of the GeoTIFF Importer and add the DATUM of interest to the list of Earth Models of SPRING. This is done through the careful editing of the file datum, located in the etc subdirectory, inside the SPRING installation directory. Despite being possibly done by the user, it is suggested that this modification be done by someone from the SPRING development team.

  • Situations where the PROJECTION defined in the GeoTIFF file does not make part of the list of Projections of SPRING:

Cancel the execution of the GeoTIFF Importer and get in touch with the SPRING development team. The addition of a new projection to SPRING requires the modification of many parts of the code and the recompilation of the whole system. Alternatively, if the GeoTIFF file was created by some other application that supports many different projections, you still have the option of remapping the image to one of the projections supported by SPRING and export it again to the GeoTIFF format.