Jökull - 01.01.2016, Page 32

Jonathan L. Carrivick et al.
Figure 2. Hillshaded Digital Elevation Models (DEMs) for 2007 (A) and 2011 (B) and DEM of difference
(DoD) between 2007 and 2011 (C). Yellow triangles are randomly placed points for comparing elevation values
in the 2007 and 2011 ALS DEMs. Black line delineates ice margin. White dashed lines in C are isolines of
zero elevation change. Enlarged panel in each highlights roughening ice surface, and expanding and thickening
of ice margin against lateral moraine and cliffs. – Skyggð hæðarlíkön (DEM) frá 2007 (A) og 2011 (B) og
mismunur þeirra (DoD) (C). Gulir þríhyrningar sýna staði þar sem hæð landlíkana á óhreyfu landi var borin
saman. Jökuljaðar er sýndur með svartri línu. Hvítar slitnar línur í C eru jafngildislínur þar sem hæð yfirborðs
var hins sama 2007 og 2011. Neðstu myndirnar þrjár sýna uppbrotið yfirborð þar sem jökullinn leggst upp að
hliðargarði og klettum við suðurjaðarinn.
data obtained on 6th August 2007 (Figure 2A). Geo-
referencing of the ALS data was achieved via the
base station receiver data as described above being
post-processed against the GPS receiver and Inertial
Measurement Unit (IMU) data from those instruments
onboard the survey aircraft and linked in real time to
the ALS system. The 2007 ALS data have mean point
density of 0.8 per m2 and they were aggregated us-
ing Inverse Distance Weighting (IDW) onto a regular
3 x 3 m grid with an estimated vertical accuracy of
±0.1 m.
32 JÖKULL No. 66, 2016