03.GIS Data and Files 2

Shapefiles require 3 specific files: .[blank_start]shp[blank_end] — shape format; the feature geometry itself .[blank_start]shx[blank_end] — shape index format; a positional index of the feature geometry to allow seeking forwards and backwards quickly .[blank_start]dbf[blank_end] — attribute format; columnar attributes for each shape, in dBase IV format

Shapefiles were developed by [blank_start]ESRI[blank_end] as a GIS-type format

The beginning of the .shp file contains a [blank_start]100[blank_end] byte header, which is something like a table of contents. The header contains the [blank_start]shape[blank_end] [blank_start]type[blank_end], and a [blank_start]bounding[blank_end] [blank_start]box[blank_end], which enables fast searching of containment/intersection.

Geometries can be of point, [blank_start]multipoint[blank_end], [blank_start]polygon[blank_end], OR [blank_start]polyline[blank_end] types, and are set in the Data Management Tools -> Feature Class -> Create Feature Class tool.

Addionally, the geometry can store: [blank_start]Z[blank_end] [blank_start]values[blank_end], or measures of [blank_start]elevation[blank_end]. In practice this is still somewhat unusual [blank_start]M[blank_end] [blank_start]value[blank_end], or measure which is generally either: the length along a line or, some kind of attribute data

The combination of [blank_start]geometry[blank_end] and Z/M data forms the different kinds of data the shapefile can store.

Technically, it is possible to include different [blank_start]geometries[blank_end] in the same shapefile, this is also currently against the “rules”, so be careful with your wording of the bet.

In ArcGIS software, a [blank_start]multipoint[blank_end] feature is a digital map feature that represents a place or thing that has neither area nor length at a given scale, and that is treated as a [blank_start]single[blank_end] object with [blank_start]multiple[blank_end] locations.

A [blank_start]multipoint[blank_end] feature is associated with a single record in an attribute table.

A [blank_start]PolyLine[blank_end] is an ordered set of vertices that consists of one or more parts. A part is a connected sequence of two or more points. Parts may be connected to and may intersect one another.

The following fields are for a PolyLine: Box - The bounding box for the PolyLine, stored in the order [blank_start]Xmin[blank_end], [blank_start]Ymin[blank_end], [blank_start]Xmax[blank_end], [blank_start]Ymax[blank_end]

The following fields are for a PolyLine: NumParts - The [blank_start]number of parts[blank_end] in the PolyLine

The following fields are for a PolyLine: Parts An array of length [blank_start]NumParts[blank_end]. Stores, for each PolyLine, the index of its [blank_start]first point[blank_end] in the points array [blank_start]Array[blank_end] indexes are numbered with respect to 0.

The following fields are for a PolyLine: Points An array of length NumPoints The points for each part in the PolyLine are stored [blank_start]end[blank_end] to [blank_start]end[blank_end]. The points for part 2 follow the points for part 1, and so on. The parts array holds the array index of the starting point for each part. There is no [blank_start]delimiter[blank_end] in the points array between parts.

Shapefiles (.shp) are text or binary [[blank_start]binary[blank_end]] and vector or raster [[blank_start]vector[blank_end]]. They are used in Arc as de facto standard.

GeoJSON are text or binary [[blank_start]text[blank_end]] and vector or raster [[blank_start]vector[blank_end]]. Used for [blank_start]OpenSource[blank_end] and [blank_start]WebMapping[blank_end].

WKT are text or binary [[blank_start]text[blank_end]] and vector or raster [[blank_start]vector[blank_end]]. Replacing [blank_start]KMLS[blank_end].

WKT - [blank_start]Well[blank_end] [blank_start]Known[blank_end] [blank_start]Text[blank_end]

KML - [blank_start]Keyhole[blank_end] [blank_start]Markup[blank_end] [blank_start]Language[blank_end]

prj.file - [blank_start]projection[blank_end] format - coordinate system and projection info; a plain text file describing projection using [blank_start]WKT[blank_end] format

The DBF file contains [blank_start]attribute[blank_end] information

DBG - [blank_start]dBase[blank_end] File and is a standard format for holding [blank_start]tabular[blank_end] data.