The Coastal Ecosystem Mapping and Media Viability Project

Field Data Collection and Remotely Sensed Ground Control There are two ways to ensure that Ground Control Points are accurate. One as used in this project, is to have a person on-site who uses a high grade GPS unit to verify the longitude, latitude, elevation and position (stand in the middle of the GCP and record its location (0). This coupled with post- processing for the purposes of this project has created an accuracy of approximately 2 centimetres. The other way is through Remotely Sensed Ground Control Points (RSGCP) which can be obtainable through satellite imagery coupled with post-processing done using an archive of confirmed GCPs nearby within the images (telephone masts, military points of interest, etc.) No RSGCP points were identified in the proposed field sites so the first option was selected. Ideally a mix of the two would be used to give the highest rate of accuracy and reduce the error level of the GPS. These discussions towards the selection of GCP methodology had a direct impact on the sites that where selected for the work. The denseness of the mangroves and the placement of the GCPs provided challenges when selecting the field sites from satellite imagery. For best image georectification GCPs should be placed in the corner and centre location of the mission area (Figure 6)

Figure 5. Type 1 and Type 2 – GCP Sheet

The Coastal Ecosystem Mapping and Media Viability Project

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