The raster formats that calculate statistics and take advantage of the skip factor include TIFF, IMG, NITF, DTED, RAW, ADRG, CIB, CADRG/ECRG, DIGEST, GIS, LAN, CIT, COT, ERMapper, ENVI DAT, BIL, BIP, BSQ, and geodatabase. A skip factor is not used with all raster formats. This will save you time because every cell is not examined. It is recommended that you use a skip factor (such as 100) when you are calculating statistics on a large raster stored in ArcSDE or a large mosaic dataset. The default is a skip factor of 1 for both row and column, which means that every cell in the raster is used in the calculation, resulting in the most accurate statistics. Setting a skip factor speeds up the process of calculating statistics by skipping pixels. There are two sets of parameters you can specify when calculating statistics: a skip factor and values to ignore. If the statistics do not exist, they can be created in ArcCatalog or the Catalog window or by using the Calculate Statistics tool. Creating statistics for rasters prior to their use in ArcMap is recommended so that you don't have to wait for the statistics to be calculated when displaying the raster dataset. You can also modify the stretch parameters in the Display section on the Image Analysis window. You can modify the stretch parameters on the Layer Properties dialog box to use the statistics from the current display extent, or you can generate the statistics for the dataset. If statistics exist for a mosaic dataset, more stretch methods are available (such as Percent Clip and Histogram Equalization). If statistics do not exist for a mosaic dataset, they are not calculated automatically when displayed in ArcMap. These statistics are temporary and are not stored with the raster dataset. For example, in ArcMap, when a raster dataset without statistics is first added to the data frame, default statistics are calculated from a subset of the dataset when they are needed to render the raster dataset. It is not always essential to calculate statistics because they will be calculated automatically when they are needed. Statistical information for mosaic datasets is stored internally. Once the auxiliary file has been created, the statistics within it will be reused for future procedures that require statistical information. Please let me know if I'm using any terms wrong or am understanding any concepts wrong.Statistics are required for a raster dataset or mosaic dataset to perform some geoprocessing operations or certain tasks in ArcGIS Desktop applications (for example, ArcMap or ArcCatalog), such as applying a contrast stretch or classifying data.įor raster datasets, the statistical information, including a histogram, is stored in an associated auxiliary file, if it cannot be stored internally. It would be very much appreciated.Īgain, I'm very new to this. I was hoping someone could attempt to add the two together the rasters I've attached below on their own ArcMap or similar software to see if indeed I've made my rasters correctly. My next exercise depends on the pa_raster layer being created from merging the two raster layers. If anyone has any advice regarding how to check that my Python is alright of if somehow my raster calculator isn't set up properly, please let me know. I've used Python 2.7.5 and 2.7.11 and both create empty file outputs. I don't know how to address that issue currently. I am pretty confident that I created my raster layer correctly and have been told by a few sources that its possibly my Python that is the problem. My raster calculator function is extremely simple: I'm supposed to use the Map Algebra function, but unfortunately, I seem to be getting an empty output every time I try. Currently, I need to merge two raster layers, one made from point data and another made from polyline, into a single raster layer. I've bought a few textbooks in a series called An Introduction to GIS in Marine Biology and am working through a few simple exercises. I'm currently learning the very basics of ArcMap 10.2.2.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |