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Comparison of OS MasterMap files sizes versus Land-Line.Plus

The following table shows the comparative file sizes between OS MasterMap Topography Layer data in various formats against the equivalent Land-Line data:

Comparison of File Sizes

Source Data	Compressed (.zip)	Uncomp	MapInfo (MIF/MID)	Shape (1)	Shape (2)	ESRI Geodatabase
Tile NN34 (4)
OS MasterMap GML (3)	5Mb	26.3Mb	21.5Mb	6.8Mb	17.5Mb	22.1Mb
Land-Line.Plus NTF	0.7Mb	2Mb	4.8Mb	N/A	2.8Mb	4.8Mb
Tile SU6352 (5)
OS MasterMap GML (3)	1.1Mb	19.1Mb	5.8Mb	5.6Mb	16.1Mb	15.3Mb
Land-Line.Plus NTF	0.09Mb	1.3Mb	2Mb	N/A	3.9Mb	4.5Mb

Notes:

• (1)Converted to Shape using MapManager Geodatabase Filter
• (2)Converted to Shape using ArcToolbox Shapefile Export
• (3)The GML data covers a slightly larger area since it is 'hairy' i.e. objects continue outside rectangular tile boundary.
• (4)This is the equivalent of 4 x 1:10,000 tiles plus 2 x 1:2,500 tiles of rural area.
• (5)This is equivalent to 4 x 1:1,250 urban tiles

Typically, it would appear that OS MasterMap is between 3 and 5 times larger than the equivalent Land-Line.Plus data, even when in it's compressed form or when converted to alternative formats.

The following diagrams show the above information graphically:

Size vs. Area

The following table gives some indicative sizes for GML data for different areas. It can be seen that the size of a dataset varies enormously depending on what type of area it is. It should also be noted that the amount of compression can vary quite significantly between datasets.

	Urban 5Km2	Rural 5Km2	Semi-Rural 5Km2
Compressed (gz)	4.5Mb	0.5Mb	0.8Mb
Uncompressed (GML)	82.7Mb	4.8Mb	11.8Mb