Differential Global Inexpensive over small study Restricted resolution and accuracy. Positioning System areas. Error increases with distance from (DGPS) Accurate to 20 mm in the reference station. vertical direction and 5 mm in Accuracy reduced due to tree cover. the horizontal direction (USGS 2000b). Airborne Laser Survey High-resolution data over a Requires independent survey over (ALS) defined area. flights. Measures the return time Can be supplied with Expensive of pulsed light to provide corresponding Prone to localised distortion if effective high-resolution aerial algorithms to remove vegetation are not topographic data photographs. applied. Over flights can be commissioned whenever the client requires (subject to weather conditions).
Differential Global Positioning System (DGPS) Inexpensive over small study areas. Accurate to 20 mm in the vertical direction and 5 mm in the horizontal direction (USGS 2000b). Restricted resolution and accuracy. Error increases with distance from reference station. Accuracy reduced due to tree cover. Airborne Laser Survey (ALS) Measures the return time of pulsed light to provide high-resolution topographic data High-resolution data over a defined area. Can be supplied with corresponding aerial photographs. Over flights can be commissioned whenever the client requires (subject to weather conditions). Requires independent survey over flights. Expensive Prone to localised distortion if effective algorithms to remove vegetation are not applied.
peat-swamp-subsidence.docx