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Learn about the fundamental limitations affecting performance in spatial data processing and explore methods to enhance efficiency. Discover the crucial factors such as data size, storage, processing type, software, and hardware availability. Explore raster and point data constraints, network access issues, ArcGIS tools, remote sensing resolutions, and raster structure dimensions for optimal results.
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Performance • Performance is fundamentally limited by: • Size of data • Where the data is stored • Type of processing • Processing software • Hardware available
Real Performance Limitations • Rasters: Size of the data and number of files • Points: Number of rows, number of size of attributes • Network access, especially services • ArcGIS tools • Mistakes in processing • Hardware
4 Resolutions of Remote Sensing • Spatial: • X and Y resolution • Spectral: • Number of bands • Temporal: • Number of samples per time unit • Radiometric: • Number of bits or bytes per sample
Raster Structure X Dimension Band 0 16 15 10 12 Band 1 23 27 14 19 Band 2 Y Dimension 29 30 18 22 34 32 21 25 Sample Pixel: All the samples are coincident
Raster Resolutions • Spatial Resolution: • Width and height of each sample/pixel • Spectral Resolution: • Number of widths of the bands • Radiometric Resolution: • Number of bits per band • Temporal Resolution: • Number of rasters per time interval
Raster Resolutions • Spatial: • 10 cm to 1 km • Spectral (Number of Bands): • 3 for photos, 7 for Landsat, for 256 MODIS • Temporal: • Daily for MODIS, 15 days for Landsat, every few years for SRTM • Radiometric (Sample Depth): • 8 bits=0 to 255 (256 shades)
Raster Size Size in Bytes = Width of the area * Resolution * Height of the area * Resolution * Bytes per band * Number of bands * Number of Temporal Slices
Landsat TM Scene • Sensor type: opto-mechanical • Spatial Resolution: 30 m (120 m - thermal) • Spectral Range: 0.45 - 12.5 µm • Number of Bands: 7 • Temporal Resolution: 16 days • Image Size: 185 km X 172 km • Swath: 185 km • Programmable: yes http://landsat.gsfc.nasa.gov/about/tm.html
Improving Performance • It used to be storing the data was a major problem • Today, the problem is getting the computer processor “close” to the data
Improving Performance • Resample rasters to the size desired • Clip rasters to the area of interest • Only use the bands required • Store or “cache” rasters to the computer doing the processing • Include performance evaluation as part of the modeling design