BASIC SPATIAL ANALYSIS TOOLS IN A GIS data set queries basic statistics buffering overlay reclassification
GIS ANALYSIS TOOLS
GIS ANALYSIS TOOLS Database tools: query and summarize (similar to spreadsheet or database program contains spatial component Grid-based: buffering, overlay and map calculator tools Image processing and terrain analysis: based on moving window that create new maps from patterns on the original
QUERIES Ask questions about GIS data set: Where are the older stands? Which roads are paved? Which trails are authorized? Which water sources are within a certain distance of a road?
QUERIES Where are the thinnable stands? Age 30 and Age 40 Age 30 and Age 40 and MBF 30
QUERIES Structured Query Language (SQL) uses standard operators e.g. = > < + - * and or not standard order of operations add/subtract before multiply/divide use parentheses to isolate terms
QUERIES Example: select stands greater than 30 acres with grass understories and a mean quadratic diameter less than 20 inches. query for above: (area > 30) and (understory = grass ) and (QMD < 20)
QUERIES Which water sources are within a certain distance of a road? Y # Y # we need more information. perhaps a new data set layer. buffering may help answer this question Y Y # # Y #
BASIC STATISTICS statistics can help determine meaning within the data simple, sum, count, mean, maximum, range, variance and standard deviation calculates statistics for a combination of fields, for example: by combining the State name field & Population fields, we can calculate the average state population
BUFFERING defining closed areas (polygons) within a certain distance of selected landscape features: to identify areas surrounding geographic features identify / select features that then fall within / outside the boundary of the buffer provide summary measures of proximity
BUFFERING you can buffer points, lines and polygons
BUFFERING What do the riparian buffer zones look like? How far around an owl nest location is 70 acres? What do the visually sensitive areas around trails encompass?
BUFFERING problems may occur when buffering very convoluted lines or areas; or for large datasets may have to increase the virtual memory of your system or break the job up into a number of smaller pieces
BUFFERING Site selection determine location of new well make sure it does not fall within 10km of chemical factories find all stream segments within 300 meter of a proposed logging area
BUFFERING Environmental pollution zone of noise pollution around major roads buffers around contaminated land to prioritise sites (according to land use, water courses & ground water protection zones)
BUFFERING Resource management / Planning service zones (e.g. 2,000 m around recycling centres) create protection zones around features (e.g. nature reserves) e.g. Bus routes
BUFFERING Epidemiology disease clusters around certain features (e.g. asthma surrounding incinerators) Crime to examine if car crime is more prominent in certain areas (e.g. close to major roads, street corners, car parks)
OVERLAY processes involving two (or more) layers merging is a simple overlay process that combines two or more layers into one. It leaves overlapping re gions and does not create new attributed polygons w here there is overlap. three overlay processes are considered here: Union Intersect Identity
OVERLAY Laying one GIS data set on another to produce a combination of the two. Union: determining the combination of two GIS data set. resulting GIS data set will extend as far as both input GIS data set extend
OVERLAY Union: What is the combination of the stands and the fire area? Input GIS database #1 Input GIS database #2 Output GIS database
OVERLAY Laying one GIS data set on another to produce a combination of the two Intersect: finding the overlapping areas between two GIS data set
OVERLAY Intersect: Where do the stands and the fire area overlap? Input GIS data set #1 Input GIS data set #2 Output GIS data set
OVERLAY Laying one GIS data set on another to produce a combination of the two. Identity: determining how one GIS data set can be modified by the position of features in another. limited to the spatial extent of the first GIS data set.
OVERLAY Identity: Where does the fire occur in the stands data set? Input GIS data set #1 Input GIS data set #2 Output GIS data set
BOOLEAN OPERATORS Definitions to retrieve geographical data essential part of most GIS projects Usages to retrieve geographical data to check the quality of data and the results obtained (i.e. hotels in the sea after digitising or data conversion) Boolean operators A AND B, A OR B, A NOT B, A XOR B, (A AND B) OR C, A AND (B OR C)
BOOLEAN OPERATORS 1 = true 0 = false A B NOT A 1 1 0 0 1 0 1 0 0 0 1 1 A AND B 1 0 0 0 A OR B A XOR B 1 1 1 0 0 1 1 0
BOOLEAN OPERATORS Venn diagrams
OVERLAY TYPES - VECTOR Point in Polygon overlay point objects on areas, compute "is contained in" relationship points a,b,c...n, are contained within polygon x result is a new attribute for each point in the data set
OVERLAY TYPES - VECTOR Line on Polygon overlay line objects on area objects compute "is contained in" relationship lines are broken at each area object boundary containing area is new attribute of each output line
OVERLAY TYPES - VECTOR Polygon on Polygon overlay two layers of area objects boundaries are broken at each intersection number of output areas likely to be greater than the total number of input areas after overlay we can recreate either of the input layers by dissolving and merging based on the attributes contributed by the input layer
OVERLAY TYPES - VECTOR
OVERLAY TYPES - RASTER very fast and easy compared to vector overlay extent of calculations is much less cell-by-cell basic new cells are assigned attributes composed from original cells condition: both layers have identical geometry quantitative or qualitative overlay less flexibility with attributes
OVERLAY TYPES - RASTER raster maps treated as arrays of numbers to be added, subtracted, etc.
OVERLAY TYPES - RASTER High slope (red) + Private land (blue) = Potential areas for a ski resort (brown)
OVERLAY TYPES - RASTER Map Algebra operators arithmetic operators: +, -, *, /, ^, grid2 = grid0 + grid1 logical operators, =, >, <, >=, <=, <>, etc. grid2 = grid0 > grid1 (grid2 becomes 1 where this is true, 0 where false) mathematical functions (trigonometric, logorithms, etc.) grid2 = sin(grid1) best raster systems allow multiple input grids grid5 = grid1 * ( grid2 + grid3 - grid4 ) Saves calculating and storing intermediate grids
RECLASSIFICATION input is result of classification grouping of attributes according to limits with no change in geometry results usually in a lower number of classes aim: to remove detail to emphasize spatial patterns visualize new pattern and connections transformation from one classification system to another (e.g. soil types to agricultural land use s uitability)
RECLASSIFICATION Household Income 0 5000 5000 10,000 10,000 20,000 20,000 40,000 40,000 60,000 50,000 75,000 > 75,000 Low Income Group Middle Income Group High Income Group
NETWORK ANALYSIS movement or distribution of resources across a connected network or arcs. routing optimum path between two locations allocating maximize capacity at a facility e.g. assign streets to fire stations address Matching locate street address along an arc based on address
SURFACE ANALYSIS three dimensional analysis (x,y,z) lattice or TIN (Triangulated Irregular Network) viewshed, profile, volume, slope, aspect not always based on elevation e.g. pollution, climate data, water table, etc
http://www.qgistutorials.com/ Before lunch -Work with SEAFDEC data -Make a nice map and some chart
Last homework for evaluate, you can do it or not Please make a nice map with your data that compose with Country boundary Any kind of point data Chart of your point data Don't forget to include your name in the map for copy right Export your map to png file Send it to psiriporn@seafdec.org before this midnight Wirotela@gmail.com
Buffering make 3000 meter protected area from shoreline of Thailand make polygon of 30km zone area buffer function difference function (real protected zone) find out which fishing boat (catch data) operate in 30km zone How many and which one???? Within query