Shapefiles (.shp)

Shapefiles are a format introduced by ESRI for the storage of geodata, which has developed into a quasi-standard for the exchange of digital geographical information. In contrast to LTG files, which contain area, line and point information, a shape file describes only one separate layer (e.g. only the boundaries of postal code areas). However, a shapefile does not consist of a single file, but of a bundle of files that are needed for the corresponding use. In addition to a SHP file for storing geometry information, this includes SHX or DBF files in which index information for the geometry or attribute data is stored.

Inserting Shapefiles in EasyMap

Shapefiles can be inserted directly from the control window Base Maps onto the map sheet. If the shapefiles to be edited are not stored in the standard path of the digital maps, the corresponding directory must be selected.

All shapefiles in the selected directory are listed in the control window Map Basics under "Maps in SHP format". To insert all shapefiles in the specified directory on the map sheet, click on the heading above the individual shapefiles and drag them with the mouse from the Map Basics control window onto the map sheet (Drag&Drop). The heading above the individual shapefiles corresponds to the name of the folder containing the shapefiles (here GK3). To insert a single layer (e.g. e-streets_-_main net), select it with a mouse click and then drag and drop it from the Map Basics control window onto the map sheet. As soon as one or more Shapefiles have been dragged onto the map sheet, the Select Key Columns window opens.

Selection of key column

In contrast to the LTG format cards included in the scope of delivery, whose key column is predefined, Shapefiles can contain several columns with different identification numbers or IDs. From these numbers and IDs, a so-called key column must be selected, which is to be used for linking the base map and attribute data. This column must have the property that it contains only unique values. Columns with empty cells or number columns with decimal places are also not valid key columns.

Each object of a shapefile always contains at least one column with the name "FID" in the corresponding table (DBF file). The abbreviation FID stands for Feature Identifier and represents a unique identification number for each object of a shapefile. However, the FID is usually a consecutive number with which the individual objects are numbered consecutively, so that the FID can only be considered as an emergency solution if no other column fulfills the conditions for a key column. For example, analyses should only be based on the data supplied from the shape file if FID is used as the lead column.

After a corresponding key column has been defined for all shapefiles, the individual shapefiles are displayed in the map sheet and in control window Content . By default only the geometries (areas, lines and points) are visible. The corresponding texts are not displayed at first, but can be made visible later by checking the corresponding box in the control window Content checkbox.

Further topics:

ClosedIndex Files for Shapefiles (.qix)

EasyMap must build a Index file (*.qix) in order to use Shapefiles. If the user has write permissions in the directory from which the shapefile comes, the generated QIX file is stored in this directory. The next time the same shapefile is used, it is reused, resulting in significantly faster processing times. If the QIX file cannot be saved, it must be regenerated each time the shapefile is used, which can lead to longer insertion times, especially with large shapefiles. If no write permissions are available and the shapefiles are used frequently, it is a good idea to move the files or use them once under a user account in EasyMap that has write permissions here (e.g. administrator).

Note: Please keep in mind that the QIX files are not automatically regenerated if, for example, changes have been made to the SHP file. It may happen that a SHP file is not displayed even though it is correctly assembled. In such a case, delete the existing QIX file and create a new one with EasyMap.

ClosedProjection files for Shapefiles (.prj)

In the basic version, the SHP format does not provide any information about the coordinate system in which the stored coordinates are stored. For this there are additional projection files (PRJ) in which this information can be stored. These are optional, but many functions are not available if the projection file is missing. A projection file has the same name as the shape file, but the extension *.prj.

Base maps can only be displayed together in a map if they use the same or a very similar coordinate system. This cannot be determined without a projection file and is therefore not possible in these cases. In addition, no conversions into length specifications can be performed.

Note: Always make sure that you also have projection files for the shapefiles used. Otherwise, the functionality is very limited.

ClosedCharacter encoding in Shapefiles

Unfortunately, there is no uniform standard for character encoding for shapefiles. This cannot even be determined from the files by the program.

If you are using a shapefile and the texts are incorrect (for example, german umlauts are displayed incorrectly, or even entire texts consist only of cryptic characters), EasyMap could not determine the character coding of the shapefile. By default, EasyMap uses the ANSI character set with the code page currently set in the system for reading shapefiles.

To define the character encoding for a shape file, ESRI has introduced another additional file, the Codepage File (CPG) . This is a text file with the same name as the Shape file, but with the extension *.CPG. The only text that must be entered in this file is the number of the code page in which the shape file was encoded.

The following code pages are frequently used:

  • 850: Western European (DOS)
  • 1252: Western European (Windows)
  • 1200: Unicode
  • 65001: Unicode (UTF8)

Especially for Eastern European countries the following code pages are used more often:

  • 1250: Central European (Windows)
  • 1251: Cyrillic (Windows)
  • 1253: Greek (Windows)
  • 1254: Turkish (Windows)

Specifying the Character Encoding for a Shapefile

EasyMap supports you in creating a code page file for an existing shape file if this is missing and characters are displayed incorrectly. In the Map Basics control window, open the context menu on a shapefile with the right mouse button and choose Define code page for file "...". In the following dialog you can define a character encoding. After completing this process, EasyMap creates a CPG file. To do this, you must have write permission in the folder in which the shape file is located. If this is not the case, contact your administrator.