The influence of pixel type\depth on the raster,
I couldn’t figure out the practical effect of the pixel type\depth on the raster. For example:
Thank you
Best
Jamal
This appears to be a rather old, unanswered question bumped to the top, but the practical effects of changing pixel type are file size and available values.
1.) 8-bit unsigned = values 0 - 255. 16-bit unsigned = 0 - 65535.
2.) 16-bit unsigned = 0 - 65535. 16-bit signed = -32768 - 32767.
The more digits (bits) your pixels hold, the larger the file size.
A heads up...the torrent of 'new' threads are the result of redirecting remote sensing and imagery related threads to their rightful home ... Imagery and Remote Sensing
Thank you guys for the useful input.
I couldn’t figure out
It's based on your requirements for pixel and limitation of file storage. An 8 bit raster will be a smaller file than 16 bit, but also have less available pixel values. If you don't care about either, then the choice is irrelevant.
Thanks Darren for the prompt help,
Does this mean that the rasters with high depth have better “appearance” as more values are offered to the cells to better represent the reality. In other words, rasters with higher depth look clearer than those of low depth value.
Is this correct?
Not really. You can degrade the appearance by reducing the original pixel depth, but you can't improve it just by making more values available.
You may be thinking about reducing the cell size and interpolating to artificially add intermediate values to an image. Of course, those intermediate values would have to be available, which is where pixel depth comes in.
What Darren said. To supplement his explanation, here is a good help resource on the topic: Bit depth capacity for raster dataset cells—Help | ArcGIS for Desktop.
A raster has four types of resolution - spatial, spectral, radiometric, and temporal. The pixel depth is under the radiometric resolution of a raster. It simply specifies how well the differences in brightness in an image can be perceived. The higher the radiometric resolution (pixel depth), the better small differences in reflected or emitted radiation can be measured. It also means that you'll have a larger volume of measured data.
However, unlike image data, computer monitor screen pixels can only have 256 unique RGB brightness values. Clearly, this limitation prevents the most of the data from being displayed with brightness exactly equal to their real value. Here you can use image enhancement like contrast stretching to achieve a better rendering of your raster.
So when to use 16-bit:
8-bit:
Just a small point of clarification, not all rasters have a spectral resolution, since not all rasters are technically measuring the EM spectrum with sensors tuned to a specific set of wavelengths. Some raster's pixel data represent categorical data, such as land cover classes, soil types, forest types, elevation classes, slope, aspect, or may even be derived from scanning a paper map. Given that I thought it was worth making this distinction. It might better be said that, "A remotely sensed image has...." .