SPOT Data Provision
There has been five SPOT (Satellite Pour l'Observation de la Terre) satellites launched since 1986, providing medium to high resolution imagery of the Earth's surface.
DIMAP
The DIMAP format is the new format for SPOT products, introduced for the SPOT 5 launch in May 2002.
The DIMAP format is a public format for describing geographic data. Although it was specially designed for image data, it can also handle vector data. SPOT products in DIMAP format now consist of two parts, one for the image and the other for a description of the image.
Find out more about the format here...
SPOT 5
SPOT 5 was launched on the May 4th 2002 and combines a significant number of new and improved features over the previous sensors.
- Better ground resolution - 5 metres ground resolution in panchromatic mode (2.5 metres in supermode)
- Higher resolution in multispectral mode - 10 metres in the visible and near infrared ranges (5 metres in supermode)
- Location accuracy better than 50m without ground control
- In coupled mode can acquire swath of 120Km
- Repeat coverage every five days (three days in European latitudes)
- High Resolution Stereoscopic (HRS) instrument will provide simultaneous acquisition of stereo pairs (600Km by 120Km) with an elevation accuracy of 10 metres
- Ortho-images from archive have an absolute accuracy of 10 metres without GCPs.
SPOT 1-4
SPOT 1, 2 and 3 carry a multi-spectral (XS) and panchromatic (Pan) sensor on board. SPOT 3 failed in November 1996, but 1 and 2 are still operational.
SPOT 4 was successfully launched in March 1998. It has similar features to the previous satellites, but offers the following advantages:
- An additional spectral band is sensed, equivalent to TM band 5 (short wave infra-red)
- An instrument dedicated to vegetation monitoring
- The Pan band has been replaced with a mono-spectral 10 metre red band
The SPOT satellites orbit at an altitude of 810Km. SPOT scene sizes are typically 60Km by 60Km (vertical viewing) or 60Km by up to 80Km for oblique viewing. The optical imaging instruments (HRVs) are steerable to either side of the ground track - east to west - by up to 30 degrees. Stereo images can therefore be acquired which are ideal for topographic mapping and the generation of digital elevation models (DEMs).
SPOT Pan data is acquired over the visible green to near infra-red portion of the spectrum, while the SPOT 4 mono-spectral band is acquired in the visible red. Both have 10 metre spatial resolution.
SPOT Pan data does provide a noticeable improvement in spatial resolution compared to the Landsat 7 ETM+ Pan band (10 metre compared with 15 metres, click here for examples). However, there is a significant cost increase with the purchase of SPOT Pan data.
SPOT XS / XI
With the addition of Band 4 (mid infra-red) on SPOT 4, the SPOT multispectral data has become more versatile, especially with regard to agriculture and forestry applications. However, Landsat is still the most appropriate data source for the majority of geological applications.
A summary of the band information is contained in the table below.
| Band Width | Spatial Resolution | |
|---|---|---|
| Band 1 | 0.50 - 0.59µm (green) | 20 metres |
| Band 2 | 0.61 - 0.68µm (red) | 20 metres (& 10m XI) |
| Band 3 | 0.79 - 0.89µm (near infra-red) | 20 metres |
| Band 4 | 1.58 - 1.73µm (mid infra-red) | 20 metres |