Layer theory

All Map Maker projects use Layers, transparent sheets of data overlaid one upon the other.

Layer Types
Layer Types

A map project can be thought of as a combination of several layers, arranged and styled in a particular way and ready for use in the field, for a presentation or for publication.

A layer on the other hand is simply a data set, with or without an underlying database, with or without styling.  A map project has a context, whereas the data may have only limited contextual information associated with it.  In other words a layer comprises a discrete set of data rather than a finished map.

Map Maker like other GIS packages uses 2 main types of map data:

Vector: polygons, lines and points, defined by a set of coordinates (x and y). Map Maker uses it’s own native format to save these data identified as .dra

Raster: digital images i.e. made up of pixel squares and save in any number of picture formats, which are not specific to Map Maker.   Most Raster data will come as a collection of tiles either maps, air photos, satellite imagery or a digitally derived data set.

In Map Maker, unlike some packages, mixing vector types within a layer is possible, but we do not recommend it.  Text and arrows are another Vector type in Map Maker, but more of this later when we talk about editing Vector data.

Raster data needs a little more information than is available in the digital image alone for it to be useful in map presentations.   Co-ordinate information is held separately in a so-called “world file”, which will have been saved alongside the .tif images as a .tfw. Without co-ordinate information, it is impossible to create tiled views or overlay other data sets correctly.  If your tiling is not working, the .tfw may be missing or corrupted.

Finally, it is possible to import a number of non-native data sets into Map Maker.  The most common one, is the .shp format (by ESRI the Makers of Arc GIS).

Map projects can combine Map Maker’s .dra format, with Arc layers (.shp) and digital image files (.tif).  It is possible to convert files from format to the other, and in some instances – large data sets – it is highly advisable to convert .shp into .dra. There are Utilities available to do this along with image manipulation.

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