Abstract

High-alpine areas are subject to rapid topographic changes, mainly caused by natural processes like glacial retreat and other geomorphological processes, and also due to anthropogenic interventions like construction of slopes and infrastructure in skiing resorts. Consequently, the demand for highly accurate digital terrain models (DTMs) in alpine environments has arisen. Public administrations often have dedicated resources for the regular monitoring of glaciers and natural hazard processes. In case of glaciers, traditional monitoring encompasses in-situ measurements of area and length and the estimation of volume and mass changes. Next to field measurements, data for such monitoring programs can be derived from DTMs and digital ortho photos (DOPs). Skiing resorts, on the other hand, require DTMs as input for planning and – more recently – for RTK-GNSS supported ski-slope grooming. Although different in scope, the demand of both user groups is similar: high-quality and up-to-date terrain data for extended areas often characterised by difficult accessibility and large elevation ranges. <br><br>Over the last two decades, airborne laser scanning (ALS) has replaced photogrammetric approaches as state-of-the-art technology for the acquisition of high-resolution DTMs also in alpine environments. Reasons include the higher productivity compared to (manual) stereo-photogrammetric measurements, canopy-penetration capability, and limitations of photo measurements on sparsely textured surfaces like snow or ice. Nevertheless, the last few years have shown strong technological advances in the field of aerial camera technology, image processing and photogrammetric software which led to new possibilities for image-based DTM generation even in alpine terrain. At Vermessung AVT, an Austrian-based surveying company, and its subsidiary Terra Messflug, very promising results have been achieved for various projects in high-alpine environments, using images acquired by large-format digital cameras of Microsoft’s UltraCam series and the in-house processing chain centred on the Dense-Image-Matching (DIM) software SURE by nFrames. <br><br> This paper reports the work carried out at AVT for the surface- and terrain modelling of several high-alpine areas using DIM- and ALS-based approaches. A special focus is dedicated to the influence of terrain morphology, flight planning, GNSS/IMU measurements, and ground-control distribution in the georeferencing process on the data quality. Based on the very promising results, some general recommendations for aerial photogrammetry processing in high-alpine areas are made to achieve best possible accuracy of the final 3D-, 2.5D- and 2D products.

Highlights

  • Mapping missions in alpine terrain are often characterized by harsh environments, limited accessibility, difficult topographic conditions and short seasons

  • At Vermessung AVT, an Austrian-based surveying company, and its subsidiary Terra Messflug, very promising results have been achieved for various projects in high-alpine environments, using images acquired by large-format digital cameras of Microsoft’s UltraCam series and the in-house processing chain centred on the Dense-Image-Matching (DIM) software SURE by nFrames

  • From the very promising results of our projects, we are convinced that DIM is an attractive alternative to airborne laser scanning (ALS)-based digital surface models (DSMs) and digital terrain models (DTMs) generation, especially for areas where canopy penetration capability is of minor importance

Read more

Summary

INTRODUCTION

Mapping missions in alpine terrain are often characterized by harsh environments, limited accessibility, difficult topographic conditions (steep surfaces, great elevation ranges, limited satellite visibility, etc.) and short seasons (bounded by weather, lighting conditions and snow coverage). Despite these challenges, mapping quality has reached a level that was not conceivable only a few years ago. While the most demanding tasks still require terrestrial (in-situ) surveying using total stations, levels, GNSS equipment or laser scanners, airborne (remote) sensing has become a serious competitor (in terms of price and quality) for small project areas, thanks to the advent of unmanned airborne vehicles (UAVs) These platforms fill the dwindling gap between in-situ missions and “classical” airborne mapping missions flown with helicopters or fixed-wing aircraft (Immerzeel et al, 2014).

Equipment
Flight planning
Georeferencing
Dense image matching
Classification and modelling
PROJECT EXAMPLES
Example 1
Example 2
Example 3
Findings
CONCLUSIONS
Full Text
Published version (Free)

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call