MITIFF

Author

ěystein God°y, METNO/FOU, 16.02.2006

W5 of MITIFF

What?

MITIFF is an implementation of geocoded information in TIFF 6.0. The difference bewteen a standard TIFF 6.0 image and the MITIFF image is the special formatting of the TIFF commentary tag. This is formatted with information required for geolocation of the image. The reason this formatting is used and not the GEOTIFF standard is that the GEOTIFF standard was not available when the MITIFF was needed. More info on the ASCII tag wil be given below.

Why?

GeoTIFF was an idea, but not a functional library when MITIFF was created. If GeoTIFF had been available, this would have been used instead.

Where?

MITIFF was developed for visualisation of meteorological raster data (e.g. satellite and weather radar data) in a meteorological work station. MITIFF is implemented in various local libraries at the Norwegian Meteorological Institute. The reference implementation is the libsatimg implementation. This is the basis for the use in DIANA. libsatimg is now being phased out and support is added to libfmio instead. Libraries are available upon request.

When?

MITIFF was defined in 1994 with only minor adjustments since tehn.

Who?

The original version was defined and implemented by ěystein God°y, adjustments have been performed together with Steinar Eastwood.

Fundamentals

TIFF 6.0

TBW

User Coordinate System

The User Coordinate System (UCS) system is the navigation system used within the USGS mapping software PROJ.4. Basically it is a Cartesian coordinate system having origo at the North Pole. Positive x-direction is eastwards and y-direction southwards in the Pacific. The following variables are used to navigate images in this system:

All distances are given for the center point of the pixels. Images are always presented in Polar Stereographic map projection correct at 60░N aligned along the 0░E (Greenwich) meridian. A graphical outline of the configuration is given below.
UCS outline

Geolocation information

An example of the MITIFF geolocation information and an explanation of the elements is given below. When presented here newline characters are also visualized.

Satellite: NOAA-16     \n 
Date and Time: 09:38 26/10-2001 \n 
SatDir: 0\n 
Channels: 5 In this file: 1 2 3 4 5           \n 
Xsize: 1000 Ysize: 1000\n 
Map projection: stere                         \n 
TrueLat: 60.00 N GridRot: 0.000\n 
Xunit: 1000 m Yunit: 1000 m\n 
NPX: 0.000000 NPY: 0.000000\n 
Ax: 1.500000 Ay: 1.500000 Bx: -266.731445 By: -2301.237549\n 
Calibration VIS: A=(0.000000)+(0.392157)*C\n 
Calibration IR: T=(323.000000)+(-0.500000)*C

The geolocation information is a specially formatted text string located within the TIFF tag for "Image description". It is composed of a sequence of keywords and data content. The keywords are not only a single word, but can also be a sentence. The keywords can be grouped in sections, not being physical sections clearly identified in the header, but sections by purpose.

The first section describes the satellite data and contains the keywords:

The second section describes the image:

The third section describes the Universal Coordinate System used both in the MITIFF and MEOS/HDF files:

The final section defines calibration information or palette image information and is not further described here.

Library reference