Data Management: QueriesOverviewSPATIAL QUERIESSpatial Queries: Selecting RecordsRESELECTRESELECT, continuedLogical ExpressionsExamplesSaving Selected Sets: writeselect v. new coverageREADSELCTRetrieving Information About your DataStatisticsStatistics example In this example, you have a polygon coverage europe containing a variable (item) area for which you want stats. No {case-item} or {output file} is used.01/15/19---UT Dallas POEC 6382 Applied GIS Software1Data Management: QueriesArcPlot commands for selecting and summarizing dataMeet certain conditions: reselect, nselect, aselect, unselectDetermine characteristics of a specified feature: identifyPerform limited statistical operations on the database: statistics01/15/19---UT Dallas POEC 6382 Applied GIS Software2Overview•The manipulation of coverages lies at the heart of ArcInfo-based GIS•The methods or commands are numerous and can be classified in many ways•There is always overlap, but basic groupings are –Coverage Query: techniques for querying existing coverages (see query.ppt)–Coverage Maintenance: creating, maintaining and modifying coverages (see covergages.ppt)–Coverage Conversion: converting from one GIS format or data model to another (see convert.ppt)–Spatial Analysis: manipulation of coverages to answer some research question or achieve some operational purpose (see analysis.ppt)•Spatial analysis techniques may be used for coverage query anmd maintenace also• We will discuss Query and Maintenance in the context of Workstation ArcInfo.–query.ppt –coverage.pptArcToolbox includes these in its Data Management component•We will cover the Conversion and Spatial Analysis commands in the context of ArcToolbox, –Conversion.ppt–Analysis.ppt01/15/19---UT Dallas POEC 6382 Applied GIS Software3SPATIAL QUERIES•ARCPLOT commands which allow the user to display and query spatial data.–Determine available data:•items•list–Meet certain conditions•reselect • nselect•aselect • unselect–Determine characteristics of a specified feature•identify–Perform limited statistical operations on the database•statistics01/15/19---UT Dallas POEC 6382 Applied GIS Software4Spatial Queries: Selecting Records When you select a table, or draw a coverage in ArcPlot, all records are contained in the active set and any commands executed will affect all the records in the table. To modify specific records, you need to place records in a subset:–RESELECT - selects a subset of records from the currently selected data set using a variety of methods -- see usage for reselect in ARCPLOT. Most popular: logical expression, graphical (box, circle, etc), and overlap.–ASELECT – when issued with logical expression, selects additional records to add to selected set-when issued alone, selects all records –UNSELECT - removes features that match a logical expression–NSELECT - switches the set of selected and unselected records.–CLEARSELECT - clear the selected set -- not automatic, must clear the selected set prior to reselecting another set unless only want a record from the currently selected set.–WRITESELECT - write the selected set into a selection file which can be read later or used to create a new coverage in ARC.–READSELECT - will read a set specified with the writeselect commandThis is critical. Normally issue before every reselect!01/15/19---UT Dallas POEC 6382 Applied GIS Software5RESELECT•Arcplot: usage reselect•RESELECT <cover> <feature_class> {logical_expression}•RESELECT <cover> <feature_class> ONE <xy | *>•RESELECT <cover> <feature_class> MANY <xy...xy | *>•RESELECT <cover> <feature_class> BOX <xmin ymin xmax ymax | *> {PASSTHRU | WITHIN}•RESELECT <cover> <feature_class> POLYGON <xy...xy | *> {PASSTHRU | WITHIN}•RESELECT <cover> <feature_class> CIRCLE <xy radius | * {radius}> {PASSTHRU | WITHIN}•RESELECT <cover> <feature_class> MAPEXTENT•RESELECT <cover> <feature_class> PARTIAL•RESELECT <cover> <feature_class> KEYFILE <info_key_file> <item> {KEYITEM <key_file_item>}•RESELECT <cover> <feature_class> KEYFILE <cover> <feature_class> <item> {KEYITEM <key_file_item>}•RESELECT <cover> <feature_class> OVERLAP <overlap_cover> <overlap_feature> {selection_distance} {PASSTHRU | WITHIN}•01/15/19---UT Dallas POEC 6382 Applied GIS Software6RESELECT, continued•RESELECT <cover > <feature_class> RANDOM <number> {PERCENT} {seed}•RESELECT <info_file> INFO {logical_expression}•RESELECT <info_file> INFO KEYFILE <info_key_file> <item> {KEYITEM <key_file_item>}•RESELECT <info_file> INFO KEYFILE <cover> <feature_class> <item> {KEYITEM <key_file_item>}•RESELECT <info_file > INFO RANDOM <number> {PERCENT} {seed}•RESELECT <image_catalog> IMAGE {logical_expression}•RESELECT <image_catalog> IMAGE ONE <xy | *>•RESELECT <image_catalog> IMAGE MANY <xy...xy | *>• RESELECT <image_catalog> IMAGE BOX <xmin ymin xmax ymax | *> {PASSTHRU | WITHIN}Logical ExpressionsItem nameEQ LENE CNGT NCGE INLT LK Item name Character string*numeric valueAND ORoperandoperatorEquals, not equal to, greater than, greater than or equal to, less than, less than or equal to, contains, not contains, in a range of values, likeMust have a space on each side of the operator, even when using equal (=) symbol e.g. State = ‘TX’*Must be in ‘single quotes’(And must use key next to Enter key)01/15/19---UT Dallas POEC 6382 Applied GIS Software8Examples•Select from coverage USA polygon features for the State of Texas:–RESELECT <cover> <feature_class> {logical_expression}–reselect usa poly state = ‘TX’ (reminder:Character strings are always in single quotes)–RESELECT <cover> <feature_class> POLYGON <xy...xy | *> {PASSTHRU | WITHIN}–reselect usa poly polygon * within (drag cursor box around Texas)–RESELECT <cover> <feature_class> OVERLAP <overlap_cover> <overlap_feature> {selection_distance} {PASSTHRU | WITHIN}–reselect usa poly OVERLAP texas poly (already have a cover named texas)•Find all buildings within 100’ of a stream–RESELECT <cover> <feature_class> OVERLAP <overlap_cover> <overlap_feature> {selection_distance} {PASSTHRU | WITHIN}–reselect bldg poly overlap stream line 100 (assumes mapunits are in feet)•REMEMBER: Once you have selected a set, all future commands act only on the selected set. To clear the selected set use the command CLEARSELECT.01/15/19---UT Dallas POEC 6382 Applied GIS