Srtm90

A Calculadora Raster permite realizar operações em arquivos raster através de expressões. A operação que vamos utilizar tem o objetivo de trocar um valor de pixel por outro, conservando os demais. A fórmula utilizada para esse processo é uma operação condicional simples para substituição de pixel no raster.

Digital Elevation Model (DEM) merupakan salah satu  model untuk menggambarkan bentuk topografi permukaan bumi sehingga dapat divisualisasikan kedalam tampilan 3D (tiga dimensi). Shuttle Radar Topographic Mission (SRTM) merupakan misi untuk membuat data topografi (DEM) dengan menggunakan sistem radar dari wahana pesawat ulang alik antariksa. SRTM memiliki struktur data yang sama seperti format GRID lainnya, yaitu terdiri dari sel-sel yang setiap sel memiliki wakil nilai ketinggian. Pada penelitian ini, data DEM–SRTM resolusi spasial 90 meter dan 1000 meter digunakan untuk menghitung sebaran temperatur di Pulau Lombok berdasarkan Lapse Rate Method (perubahan suhu terhadap ketinggian tempat).

As rampas de cores são recursos amigáveis para colorir um MDE ou uma banda em falsa cor. O que muitas pessoas não sabem é que o QGIS possui uma extensa galeria de cores para representação de diversos temas.

Fiz um teste de representação topográfica para o SRTM e os resultados são bem interessantes.

http://www.processamentodigital.com.br/

Digital Elevation Model (DEM) vertical accuracy is usually achieved by its comparison with elevation of well-defined Global Positioning Sys-tem (GPS) ground control points. This accuracy varies spatially because of the various sources, from which they were derived, thus warrants the need for specific testing of their level of compliances for geomatic applications. This paper therefore investigates the quality of vertical accuracy of two DEMs covering Ondo state Nigeria. The DEMs which are currently dataset of choice from; Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) and Shuttle Radar Topographic Mission (SRTM), were assessed based on two independent GPS ground control points from two regions of the state. From the statistical analysis carried out, it was observed that in the mountainous region A, the Root Mean Squared Error (RMSE) was quite small for SRTM DEM; ±7.75 compared to ASTER DEM; ±12.72, while in the less mountainous region B, it was ±14.48 for SRTM and ±13.25 for ASTER. A 3D model of both DEMs compared with the referenced GPS data, revealed that ASTER DEM projects terrain features better than SRTM DEM. The results from both assessments revealed their level of suitability for geomatics application for the concerned region of the State.

The 2011 Tōhoku earthquake, also known as the “Great East Japan Earthquake”, (Japanese: Higashi Nihon Daishinsai) was a magnitude 9.0 (Mw) undersea megathrust earthquake off the coast of Japan that occurred at 14:46 JST (05:46 UTC) on Friday, 11 March 2011. Simulations of the inundated and devastated areas  of the tsunami were conducted using data from Shuttle Radar Topography Mission (SRTM; 90m-3 arc second resolution). Digital elevation models (DEM) draped with Landsat TM (pre-disaster) images were produced, onto
which tsunami/sea-level heights were simulated at scenarios of 1-meter, 3-meters, 5-meters, 7-meters, 10-meters,
12-meters, 15-meters, 17-meters and 20-meters, along coastal towns of northeastern Japan. Validation and accuracy
assessment of resulting coastal (simulated) inundations were done and were visually compared with the postdisaster
images of the actual tsunami-devastated areas. The simulated inundation scenarios show considerable
accuracies. The technique may have promising applications on tsunami/coastal hazard zoning, as well as, forecasting sea-level rise scenarios.

Shuttle Radar Topographic Mission (SRTM) and ASTER Global Digital Elevation Model (GDEM) provide topographic data in a global scale which are freely available for users. The potential use of these datasets for many forestry applications is highly depending on the accuracy of the datasets. In this study, we evaluated the accuracy of SRTM and ASTER GDEM version 2 with high accuracy topographic data of Light Detection and Ranging (LiDAR) acquired using Riegl LMS-Q560 sensor. This study is conducted in tropical montane forest area of approximately 3,600 hectare, Malaysian Borneo. We resampled both the SRTM (90m resolution) and ASTER GDEM (30m resolution) with bilinear interpolation and cubic convolution method to one, two and five meter pixel resolutions. The evaluation was divided into two sites; site 1 (2,100 ha) and site 2 (1,500 ha). The SRTM (SD=9.0m-10.4m; RMSE=9.3m-10.6m) was found to produce better topographic data in comparison with ASTER GDEM (SD=16.9m-18.7m; RMSE=17.0m-19.3m). Our result revealed that resampling using cubic convolution performs only slightly better than bilinear interpolation method (when compared for all SD and RMSE values) for SRTM. Resampling to higher spatial resolution (i.e. 1m) did not influence significantly the performance (when compared for all mean, standard deviation and RMSE values).

German Aerospace Centre released TanDEM-X 90 m (TDM90) global digital elevation model (GDEM) as freely available in October, 2018 and declared that it describes all Earth's landmasses pole to pole with 1 m absolute height accuracy which could not been achieved by previous space-borne GDEMs. In this study, the coherence level of TDM90 with SRTM90 and ASTER90 were comprehensively analysed by visual and statistical comparison approaches in two study areas including different topographic characteristics. In visual approaches, colour-scaled coherence maps, contour maps, aspects depending on ascending and descending flying orbits and outlier illustrations were generated and interpreted. In statistical approaches, horizontal and vertical absolute and relative geolocation disparities and frequency distributions of height differences were presented. The results demonstrated that the terrain slope has a great impact on the coherence levels between TDM90 and compared GDEMs. Overall, TDM90 is more coherent with SRTM90 against ASTER90 except clear dissimilarity problems in strip border lines. ARTICLE HISTORY

The present research study assesses the accuracy of the SRTM X band DEM with respect to high accuracy photogrammetric Digital Elevation Model (DEM) for parts of the Himalaya. The high resolution DEM was generated for Manali and nearby areas using digital aerial photogrammetric survey data of 40 cm Ground Sampling Distance (GSD) captured through airborne ADS80 pushbroom camera for the first time in Indian Himalayan context. This high resolution DEM was evaluated with Differential Global Positioning System (DGPS) points for accuracy assessment. The ADS80-DEM gave root mean square error (RMSE) of ~<1m and linear error of 1.60 m at 90% confidence (LE 90) when compared with the DGPS points. The overall RMSE in vertical accuracy was 73.36 m while LE 90 was 75.20 m with regard to ADS80 DEM. It is observed that the accuracy achieved for part of Himalayan region is far less as compared to the values officially claimed. Thus, SRTM X band DEM should be used with due care in mountainous regions of Himalaya.