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GIS Programming and CustomizationGIS 6103 - Fall 2016School of Forest Resources and ConservationGeomatics Program________________________________________________________________________________________________________Assignment 9: Polygon Geometrydue: Nov 18, 11:45amTask: To convert points into multipart polygons.Preparation: Unzip the attached file, open the attached mxd file and add the two shapefiles to the project. In VisualStudio create a form that contains a list box, two comboxes, two labels, and two buttons (see figurebelow).GPS point shapefile:The GPS point shapefile contains points collected on boundaries of street blocks (labeled “L...” in the Polygon field, with “L” standing for “Land”). For some of these street blocks, points were also taken alongside a lake (labeled “W...” in the Polygon field, standing for “Water”) inside the street block. To facilitate construction of multipart polygons and correct computation of areas, the sequence of land polygon GPS points is in clockwise direction, whereas for lakes it is in counterclockwise direction. If a street block has a lake inside, the two groups of points share the same number in the Polygon field, such as “L2” and “W2”. The polygon for such a street block needs to consist of two rings, one outer and one inner ring.Functionality:Once the form is opened by the user the code should loop through the table of content (TOC) and search for a GPS point layer (“GPS”) and for the polygon layer (“LandPolygons”) using string matching. Once foundthe names of both layers should be added to upper and lower combobox, respectively. The code should be flexible to access these two layers independent of their location in the TOC.Once the user clicks the “Compute Polygon” button the code should perform the following: 1)Remove all polygon features from that LandPolygons layer.2)Your code constructs a ring feature for land based GPS points that share the same “Polygon” value. If a lake is present, it creates also a ring feature.3)Create a polygon from each individual ring or ring pair, respectively. The polygon consists of only one ring if the land polygon has no lake, but it consists of two rings if a water polygon is associated with a land polygon. 4)Each polygon should then be added to the LandPolygons layer.5)For each polygon, access its area and report it back in the list box. By default, ArcGIS will only countthe area between the outer and inner ring for multipart polygons, i.e. the “true” land area after subtraction of the area of the hole (the lake in this case). 6)For each polygon, the street block name (L1, L2, etc.) as well as the computed area should also be written in the corresponding fields in the LandPolygons layer. The second button is to close the form.1
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