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A Digital Elevation Model of the Lövåsen Esker
University of Gävle, Department of Technology and Built Environment.
2007 (English)Student paper second term, 10 points / 15 hpStudent thesis
Abstract [en]

The threats imposed by the ongoing climate change become successively more clear. In the municipality of Sandviken the possible rise in water level in the lake Storsjön might cause major problems. This study aims to produce an elevation model over one of the threatened areas so that the effect of different water levels in the lake can be studied in the future.

The area of study consists of an esker cutting straight through the lake Storsjön. The area is densely populated and the size is about 13 hectares.

Measurements were performed, both with GPS, utilizing Network-RTK, and with total station. The formations of the ridge were captured by following the breaklines with a point density of 225 points/ha as an intended goal.

The GPS measurements were transformed into the local coordinate system of Sandviken municipality. The measured coordinates for six control points were compared to the true coordinates. The fit was not perfect, so a Helmert transformation was performed on the plane coordinates. The accuracy of the measurements was below 50 mm after the transformation. Net adjustments in plane and height were performed on the total station measurements. The error ellipses for the station points varied from 2 to 44 mm. The over all point density achieved was 274 points/ha.

Two elevation models were created, one Triangular Irregular Network (TIN) and one interpolated model using a kriging interpolation. Contour lines from both models were produced and compared with each other. The TIN creates a more angular surface and therefore the contour lines are not as smooth as in the interpolated model. Both models showed good resemblance compared with the original data.

Abstract [sv]

Problem relaterade till klimatförändringar blir alltmer uttalade. I Sandvikens kommun kan problem uppstå om vattennivåerna i Storsjön stiger. Syftet med det här examensarbetet var att skapa en höjdmodell över ett av de utsatta områdena för att effekter av en eventuell vattennivåhöjning skall kunna studeras i framtiden.

Området består av en rullstensås som sträcker sig rakt igenom Storsjön. Området är tättbefolkat och ca 13 hektar stort.

Mätningarna utfördes med både GPS och totalstation. Vid GPS-mätningarna utnyttjades Nätverks-RTK. Åsens formationer fångades genom att följa brytlinjer med en estimerad punkttäthet på 225 punkter/ha.

GPS-mätningarna transformerades till Sandvikens lokala koordinatsystem. De mätta koordinaterna för sex kontrollpunkter jämfördes med de sanna koordinaterna. Eftersom de mätta värdena inte passade in perfekt så utfördes en Helmerttransformation av plankoordinaterna. Noggrannheten på mätta värden var inom 50 mm efter transformationen. Nätutjämningar i plan och höjd gjordes på totalstationsmätningarna. Felellipserna för stationspunkterna varierade mellan 2 och 44 mm. Den sammanlagda punkttätheten uppgick till 274 punkter/ha.

Två höjdmodeller framställdes, en TIN-model (Triangular Irregular Network) och en interpolerad model där interpolationsmetoden kriging användes. Höjdkurvor framställda från respektive modell skapades och jämfördes med varandra. Ett TIN ger en mer kantig yta vilket återspeglas i höjdkurvorna som inte är lika jämna som de från den interpolerade modellen. Båda modellerna visade god överensstämmelse med originaldata.

Place, publisher, year, edition, pages
2007. , p. 22 + bilagor
Keywords [en]
surveying, DEM, elevation model
Keywords [sv]
mätning, DEM, höjdmodell
National Category
Environmental Analysis and Construction Information Technology
Identifiers
URN: urn:nbn:se:hig:diva-234OAI: oai:DiVA.org:hig-234DiVA, id: diva2:119783
Uppsok
teknik
Supervisors
Examiners
Available from: 2007-12-06 Created: 2007-12-06

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