Mapfile structure

Comments

Any text after a # is a comment. Use comments a lot to document your mapfile.

Objects or Groups

A mapfile is composed of several objects. Each object start by the keyword object and finishes by END. Inside an object there can be several objects with the object starting by its keyword and finishing by END.
A mapfile starts by the keyword MAP and finishes by END

A word on colors

The keyword COLOR, OUTLINECOLOR,.. specify the color in the RGB color space. The first value is the red intensity from 0 (no red) to 255, the second value is the green intensity from 0 (no green) to 255 and the last value is the blue intensity from 0 (no blue) to 255. A COLOR 0 0 0 indicates black while COLOR 255 255 255 indicates white. COLOR 0 255 0 would be pure green. The 3 values are compulsory and must be numbers. To select some correct values, use a color selector like the one inside MS-Paint in accessories. You select the color and the RGB values are indicated.

Mapfile header

The mapfile header is composed of several objects for the representation of the maps on the screen, you have the map itself, the web object to define how the web image is created, the reference or overview, the scalebar, the legend and if the map should be queryable. It is better to use pre-canned header and modify little parameters to conform to a specific map.
This is the standard header for a map object

Map object

Web

This group defines where to store information on the server and how to provide it to the web browser

Metadata

VIEW

View allows you to create views so you can quckly move to the geographic location, for instance moving from one country to another one.

Cf. Maps MapView for a detailed description.

Reference

This group defines how the overview should be displayed. You use an image representing the area of interest and you specify the coordinates of the location of the edge of the image. The system will draw on the image a rectangle based on the current view, indicatin the boundaries of such view.

Legend

The legend is linked to each LAYER by the way each object type is represented (POINT, LINE, POLYGON,...) and its COLOR and OUTLINECOLOR and by the NAME used in the CLASS group. It is important to have a meaningful NAME for each CLASS group in every LAYER group. The NAME of the CLASS can be different from the NAME of the layer as a LAYER can have several CLASSes.

SIZE MEDIUM

COLOR 0 0 89

Scalebar

It is interesting to display a scalebar to get information on distances.

SIZE SMALL

Query

This group secify that the map will be queryable and how the selected objects should be represented. Include this group even if you don't have a LAYER that can be queryable. It will certainly come later.

Layers

Vector layer

Let's start by a very simple layer that we will add more features to it. A layer start by the keyword LAYER and finishes by END. It can include CLASS groups, METATADATA groups. For a vector layer the CLASS is compulsory.

Layer Type

The two main types of GIS vector are ESRI shapefiles of Mapinfo TAB files. ESRI shapefiles are natively supported while the Mapinfo filesare supported via the OGR library.
All locations of files must be indicated in relative reference to the path indicated by the keyword SHAPEPATH in the MAP group.
If you have a file in "/var/www/html/map/data/mylayer.shp and SHAPEPATH indicates "/var/www/html/map/" then your file location must be "data/mylayer.shp". Using this convention allows you to easily locate files when you upload them using Maps->Layer Management.
File names are case sensitives and spaces in file names must be absoutely avoided. The extensions used for files in layer must stay with the same case sensitivity. A shapefile is usually made of a shp, idx, dbf files while a Mapinfo layer is made of TAB, ID, MAP, DAT (and sometimes IND) files.

Shapefile

Mapinfo TAB

The difference with a shapefile is the use of the OGR library to read the Mapinfo files. The keyword CONNECTIONTYPE OGR must be used and the location of the file is given by the keyword CONNECTION instead of DATA. All the rest stay the same.

Query

To make the layer queryable add anywehere inside the LAYER object the following lines:

Labels

You can use querying to know which fields a GIS layer contains. From these fields you can select on to be used a object labels in the map. For instance you have a GIS layer which contains country names. The name of the country is in the field "NAME". You will use LABELITEM "NAME" to tell the mapserver which field to use for labels.
Inside the CLASS object, you would specify how you want the labels to be rendered. For instance in our example the layer would look like this:

Thematic Mapping

Each layer contans one or more CLASS. The CLASS defines how each object should be drawn on the screen. by using CLASSITEM, you can use one field to separate objects in classes. For instance all the bathymetric lines which depth is between -100m and -500m belong to one class while each bathymetric lines which depth is between -500m and -1000m belong to another class. The separation into CLASS is made using an EXPRESSION in each CLASS. The EXPRESSION uses simple logic based on the field in CLASSITEM.
For instance in the example below we use the field "value" which contain the water depth of the LINE object to display this line object in various colors depending of the depth. If the EXPRESSION is true then the parameters in the CLASS apply. A CLASS without an EXPRESSION is a default CLASS for all the objects which have not been classified otherwise.

Metadata

Inside a LAYER group you can have a METADATA group. Some of this metadata is used for special purposes inside tikiwiki. There is only one METADATA group inside a LAYER group.

WIKI

Using WIKI creates a link from the layer name to a wiki page. Use the wiki page to indicate some information on the layer:

• custodian
• ownership
• date of creation
• accuracy
• history
• datum/projection
• interesting layer features
• ...

DOWNLOAD

If DOWNLOAD is set to "T" then the files that forms the layer can be downloaded by a registered user.

Raster layer

The easiest way to handle raster layers is to use Geotiff images which contain projection information. However making geotiff images may need advanced remote sensing software. The other way is to use an additional file which contains information about the coordinates of the pixels in the image file.
When several images are used instead of using a layer for each image they can be tiled. A shapefile is created with a rectangel for each image which helps the system to find the right image for the right location.

Geotiff

Using a geotiff image in a layer is simple, the TYPE RASTER is used with DATA pointing to the tiff file. the keyword OFFSITE is used to define which color in the tiff image should be used for transparency. This is useful when tiling or overlapping several images.

Image Tiles

Images tiles are created using utility tools from the mapserver software. The utility is called gdaltindex and parses mainly geotiff images to get their boundaries and create a shapefile containing an outline for each of the images. Under Maps->Layer Management, at the bottom of the page a utility is avalilable to generate the shapefile. Basically upload the images to the right directory. The images should have the same name prefix. Then reference all these images with a wildcaard and name the shapefile to be created. For instance you can upload coralcoastsigatoka.tif, coralcoastmomi.tif, coralcoastnavua.tif and reference them as coralcoast*.tif and create the shapefile img_index.shp

Grid Layer

A grid layer allows you to draw a grid in the local cordinates on your map. It is useful to find location of objects on the map. For best effect the grid must be the last layer in the mapfile to be drawn the last.