On the quality checking of the airborne laser scanning-based nation wide elevation model in Finland, submitted to ISPRS

Nationwide airborne laser scanning (ALS) has been carried out in European countries such as the Netherlands and Switzerland; in Germany large parts of the country has been scanned and the work is going on as federal basis. The decision makers of national mapping agencies are realizing the benefits of ALS, e.g. significantly improved accuracy, lower processing costs and higher automation, and, thus, plans of performing national laser scanning are planned in many other countries. The elevation model working group of the Ministry of agriculture and forestry of Finland recommended the usage of airborne laser scanning for the creation of a new multi-purpose nationwide elevation model in 2006, and thus the National Land Survey of Finland (NLS), in co-operation with the Finnish Geodetic Institute (FGI) had a more than 1000 km2 practical test on using ALS for the new nationwide elevation model and its quality checking in late 2006 and early 2007. The objectives of the test were: a) to define the elevation quality of ALS flights from two point densities 0.5-1 and 0.1 points per square metre resulting in two flight altitudes 2000 m and 5000 m using the Optech ALTM 3100 and scanning angle of ±20 degrees and Leica ALS50-II and scanning angle of ±20 degrees, b) to compare the quality derived with two different sensors (Optech ALTM 3100 and Leica ALS50-II), c) to define the quality of ALS derived DEM in various surface types, d) to analyse the planimetric errors, and e) to develop methods to derive ground reference data effectively