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Nur Aisah Ab.Moin / JOJAPS – JOURNAL ONLINE JARINGAN COT POLIPD
The findings from the interview can be analyses that the derived DEM from LiDAR, IFSAR and SRTM is reliable for GIS
application in hydrology. From the first experts interview, Mr. Ahmad Zuhdi Ismail declared that LiDAR and IFSAR is suitable
for delineation watershed in generating catchments and stream networks but LiDAR represent better than IFSAR. LiDAR and
IFSAR also suitable for floodplain management and flood forecast application. SRTM is not suitable for floodplain applications
but can be used for generating the catchments.

The second expert opinion, Mr. Kamarul Azlan Mohd Nasir also expressed that IFSAR and LiDAR very suitable for the
condtruction of the DEM. Nevertheless to obtain high precision data value, site investigation should be carried out as sometimes
there are doubts in data acquisition. However, he also agreed that the SRTM data are not suitable for floodplain and generating
the stream networks but are appropriate to generate the catchments

5. Conclusion

The understanding of surface topography is the major concerned in the earth sciences. The availability of topographic data
worldwide has improving the research on the world phenomenon. However with difference sources of data, the major discussed
is how accurate the data for the certain applications and the cost of data acquisition. Nowadays, the advance technology in
mapping has improving the accuracy in data acquisition. The suitable of method with desire application will give the best cost
estimation.

GIS has become a very useful tool in hydrology especially in water management. GIS able to model the spatial data of
hydrological data such as delineate watershed. The watershed can be determine with using DEMs and hydrologic data. Some
limitation occurs especially the data processing with using different software. Global mapper is easy to use due to adapted
variety of format data, while ArcGIS is limited for ESRI format only. However the software have their own capabilities. To
reduce the time of data processing, the data have to divide in a part. Although LiDAR is affordable to users but the cost of data
collection and the effectiveness of raw data processing is a big challenging.

Base on the overall results can be summarized that IFSAR data is suitable for the hydrological analysis with the DEM and
watershed analysis. The DEM resolution of IFSAR data is 5 meter. However for small area the data has some inconsistency
compared to large area. The relative accuracy shows that the 30 meter resolution of SRTM data still capable in representing
watershed and stream networks with different below than 3 meters in low elevation data. The final result shows that the lower
resolution of DEM will give less accuracy especially in low elevation data. The results proven that SRTM data insufficient for
delineate watershed in low elevation area.

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