Bitmaps are digital images, typically an image of a map, drawing or aerial photograph.  These can be loaded into NoiseMap to provide a background to a noise model or noise contours which can be overlaid onto them.  It is also possible to create a model by tracing over the bitmap image in NoiseMap.

In order for the bitmap to appear in the right position on the noise model, it must be ‘calibrated’, which is a process of adding its co-ordinates and scale.  NoiseMap provides a tool for adding this calibration.

Some bitmaps are already supplied with their co-ordinates so do not require calibration.  These are sometimes called ESRI ArcView ‘World’ files and are supplied in two parts, the ordinary bitmap (which has the suffix .bmp) and a calibration file with the suffix .bpw

Pictures in jpeg format cannot be read directly by NoiseMap: they first need to be converted into .bmp files, which many photo editors can do.  They may also be supplied with a ‘world file’ which has the suffix .jpw.  It is usually possible to use this ‘world file’ with the .bmp file simply by changing the suffix from .jpw to .bpw and loading this into NoiseMap.