Lecture 5 Raster Data Analysis

Introduction Analysis with raster data is simple and efficient for it’s feature based on position Analysis with raster data is simple and efficient for it’s feature based on position Analysis with raster data can be in a single, group, cell Analysis with raster data can be in a single, group, cell The algorithm in raster data analysis is different from that in vector data The algorithm in raster data analysis is different from that in vector data

Environment Range Range specific grid give specific grid give region by max and min coordinate region by max and min coordinate cell combined cell combined  merge  intersection mask grid mask grid Input grid Input grid More than or equal to the input grid size

Local function Single cell Single cell Not related to neighbor cell Not related to neighbor cell No effected by neighbor cell No effected by neighbor cell New grid New grid

Mask grid A region that exclude no data cell A region that exclude no data cell Data query and reclassification Data query and reclassification No data is not zero volume in cell, zero is efficient data, the region which is no data is lack of data No data is not zero volume in cell, zero is efficient data, the region which is no data is lack of data

Local function (Cont.) Arithmetic operation Trigonometric function logarithm power U= f (A, B,…) A A B C U U

Local function (Cont.) Numerical data Numerical data max, min max, min mean, sum mean, sum standards derritations valuefield standards derritations valuefield measure measure majority majority minority minority variety variety

Local function (Cont.): Combination : 0-20% 2: 20%-40% 3: >40% North: 1 East : 2 South : 3 West : 4 Combine code Slope and aspect 1 3，33，3 2 2，32，3 3 2，22，2 4 1，21，2 5 2，42，4 6 1，41，4 7 3，13，1

Local function in ArcView Cell statistics Map calculator

Application of local function in raster data Universal soil loss equation (USLE) Universal soil loss equation (USLE) A = R K L S C P A ： average loss of soil 平均土壤流失量； R ： rainfall intensity K ：土壤可蚀性 L ： length S ： slope C ： cultivation factor P ： preserve measure in water and soil

Neighborhood function Method involving a square window over the surface and computing a new value of the central cell of the window Method involving a square window over the surface and computing a new value of the central cell of the window Elements of neighborhood functions Elements of neighborhood functions central point central point size and shape of neighborhood size and shape of neighborhood function function Only in single layer Only in single layer Moving windows scan all cells Moving windows scan all cells

Neighborhood function: size and shape of neighbor

Functions of neighbor operation statistics max, min max, min mean, sum mean, sum standards derritations valuefield standards derritations valuefieldmeasure majority majority minority minority variety variety

Application of neighbor operation: data smooth

Application of neighbor operation: variety

Loop pass filter Application of neighbor operation: filter High pass filter

Application of neighbor operation: terrain analysis on DEM

Distance measurement Calculate distance from the given grid cell to source cell Calculate distance from the given grid cell to source cell same layer same layer global and extend neighbor operation global and extend neighbor operation Type of distance Type of distance nature distance nature distance cost distance cost distance

Distance measurement: rules X Grid Cell Grid Cell

Distance measurement: nature distance Unit is grid size Unit is grid size Types Types Application in ArcView Application in ArcView Continuous ： Find Distance Continuous ： Find Distance neatest ： Assign proximity neatest ： Assign proximity

Nature distance measurement

Cost distance measurement

Cost distance measurement (Cont.) Source matrix, cost matrix and link cost matrix Source matrix, cost matrix and link cost matrix Constitution of cost matrix Constitution of cost matrix sum of different costs sum of different costs Link cost matrix calculation Link cost matrix calculation horizontal: mean horizontal: mean diagonal: meanX1.414 diagonal: meanX1.414

Cost distance measurement (Cont.): link cost matrix calculation

Cost distance measurement (Cont.) Aim: to find minimum accumulative cost path Aim: to find minimum accumulative cost path Method: loop Method: loop Example: Example: Source matrix Source matrix Cost matrix Cost matrix Link matrix Link matrix Assign matrix Assign matrix Output matrix Output matrix

Minimum accumulative cost measurement B A Source matrix Cost matrix

Minimum accumulative cost measurement (Cont.) Link matrix

Minimum accumulative cost measurement (Cont.) 1.5B A

Minimum accumulative cost measurement (Cont.) 1.5B A

Minimum accumulative cost measurement (Cont.) B A

Minimum accumulative cost measurement (Cont.) B A

Minimum accumulative cost measurement (Cont.) B A

Minimum accumulative cost measurement (Cont.) B A

Minimum accumulative cost measurement (Cont.) B A B A Minimum accumulative cost matrix Cell assign matrix

Minimum accumulative cost in ArcView CostDistance: aGrid.CostDistance aGrid.CostDistance (costGrid,DirectionFN, allocationFN, maxDistance) (costGrid,DirectionFN, allocationFN, maxDistance)CostPath aGrid.CostPath aGrid.CostPath (distanceGrid, directionGrid, ByZone) (distanceGrid, directionGrid, ByZone)

Zonal Zonal function operats on properties of the region (or zone) to which a give cell beloges Zonal function operats on properties of the region (or zone) to which a give cell beloges These properties might be These properties might be length area or shape length area or shape number of location having a certain attribute value on one grid that occurs within the area define by a region on another grid number of location having a certain attribute value on one grid that occurs within the area define by a region on another grid

Zonal function in ArcView Single grid Single grid Map Calculator Map Calculator aGrid.ZonalGeometry (aGridGeomDescEnum) aGrid.ZonalGeometry (aGridGeomDescEnum) Area of a zone: Area of a zone: #GRID_GEOMDESC_AREA #GRID_GEOMDESC_AREA Perimeter of a zone: #GRID_GEOMDESC_PERIMETER Perimeter of a zone: #GRID_GEOMDESC_PERIMETER Thickness of a zone : Thickness of a zone : #GRID_GEOMDESC_THICKNESS #GRID_GEOMDESC_THICKNESS Characteristics of an ellipse that is fit to a zone : Characteristics of an ellipse that is fit to a zone : #GRID_GEOMDESC_CENTROID #GRID_GEOMDESC_CENTROID Only be useful to reclassify raster data Only be useful to reclassify raster data Requirement outcome of function is to return a corresponding parameter grid Requirement outcome of function is to return a corresponding parameter grid

Zonal function in ArcView (Cont.)

Zonal function in ArcView (Cont.) Multilayer Multilayer Input: statistics of grid data, 分带格网 Output: classify table, histogram, area statistics Steps: Summarize Zones Summarize Zones Histogram by Zone Histogram by Zone Tabulate Area Tabulate Area

Zonal function in ArcView (Cont.) According to drainage area to stat. rainfall

Zonal function in ArcView (Cont.)