Image Processing & Data Analytics

Most types of raw satellite imagery require some type of geometric correction or rectification so that the image corresponds to real world map projections and coordinate systems. Geoimage’s internal processing team can provide a range of services to correct and enhance your raw satellite imagery.

These corrections may include:

Orthorectification: Geometric rectification improves the horizontal positional accuracy of the imagery by warping the imagery to match the client’s vectors or accurate ground control, and is suitable where the area is largely flat and the imagery has been acquired from nadir (near vertical) viewing.

Pan-sharpening: Most of the VHR and medium resolution satellites now capture data in one high resolution panchromatic band and several lower resolution multispectral bands where the pixel size of the multispectral data is a multiple of the pixel size of the pan band. Geoimage has perfected the technique of merging such datasets to produce a colour image showing the better detail of the panchromatic image. The client therefore receives a colour image, which is better suited to a range of applications, such as vegetation mapping, or simply as a backdrop to vectors, with the higher spatial resolution allowing the client to see more detail.

Example of pansharpening over Brisbane

Deglinting: VHR satellite imagery over aquatic areas often exhibit water-surface-reflected sunlight along the slopes or crests of waves generated by surface winds. The effects of this “glint” can be enhanced by the collection of imagery at large off-nadir angles. Techniques involving the estimation of the glint using near infrared bands have been developed and can be applied to the data to enhance the information in the visible bands

 

Example of deglinting over Port Moresby – Image from Maxar

Example of Deglinting over Dingo Reef – Image from Maxar

Haze removal: Haze and smoke on images is a common problem in some areas of the world where the local farmers burn off after harvesting. The very high-resolution operators do not consider that haze is sufficient to exclude the purchase of new capture imagery using the 15% cloud rule. Geoimage has developed techniques to lessen the impact of the haze in colour imagery.

 

In this example of Quickbird imagery from Ghana, there are three date strips of imagery with only the western strip being affected by smoke. In the final mosaic (bottom) , the impact of the haze has been reduced as much as possible.- Imagery from Maxar

Calibration: In remote sensing applications, the most common use of calibrated satellite data is to facilitate change detection of multi-temporal images.

 

Bathymetry: Bathymetry is the calculation of water depth using satellite derived imagery. Geoimage does this by using different rates of sunlight attenuation between blue and green wavelengths, then regression to known depth control.

 

Murion Island original imagery

Murion Island Bathymetry DEM

Murion Island Bathymetry DEM with contours

Mosaicking: Mosaicking is the process whereby two or more images are seamlessly merged to look like one large image. Geoimage has used mosaicking to capture the whole of NSW twice a year since 2012.

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