The ArcPad Team Blog

Unofficial stuff from the team behind the World's leading mobile GIS platform

Thursday, August 24, 2006

Performance Tips # 1 : Shapefile drawing speed tuning with greeking

ArcPad 7 users are already experiencing faster shapefile layers drawing than previous ArcPad versions. The performance gains come from a number of design improvements; one of which is known as ‘greeking’ and is an area of performance you can further tune.

The term greeking comes from the publishing world and is frequently used to describe the process of displaying graphics and text with approximated symbols. Such is the case when the resolution of the map display is not sufficient to fully draw features that are very small at the current map scale, instead a simplified approximation of the feature is drawn.

You can enable and disable greeking using the Display Quality tab in ArcPad’s Options dialog.
Further tuning is possible by editing ArcPadPrefs.apx and changing additional parameters related to greeking. The default parameters have been carefully chosen and work well for most situations. There still may be cases where you wish to further tweak the defaults for enhanced performance or display quality to suit your specific application needs.

The simplest technique of editing the additional greeking parameters is to open ArcPadPrefs.apx in ArcPad Studio. Look for the GREEKING branch in the tree. From here you can modify the parameters for each feature type.

Tip: You can just drag the file from Windows Explorer and drop it onto the ArcPad Studio window.

For each feature type you will see there are a number of thresholds. Altering these values will change the rules for when and how ArcPad will greek features in the layer. The parameters you most likely will tweak are the threshold values. As a general rule, each threshold will have a greater value than the one before. ie.

threshold1 < threshold2 < threshold3 < threshold4

Note the not each threshold value has meaning for each feature type.

The parameters related to greeking are all described in the ArcPad Studio Help file and should be referred to before making any changes.

Experiment with different setting and study the effect when a shapefile is drawn at differing scales. Typically the effects are most dramatic when a shapefile layer has many features and is being drawn zoomed out (larger scale values).

You should also test the parameters on your mobile devices to study the effects before wider deployment.

Example of greeking preferences stored in ArcPadPrefs.apx

… other preference elements …
<POINT greeking="true" color="Gray" threshold1="0" threshold2="0" threshold3="0" threshold4="0"/>
<POLYLINE greeking="true" color="Gray" threshold1="2" threshold2="5" threshold3="9" threshold4="0"/>
<POLYGON greeking="true" color="Gray" threshold1="1" threshold2="2" threshold3="5" threshold4="9"/>
<MULTIPOINT greeking="true" color="Gray" threshold1="3" threshold2="8" threshold3="0" threshold4="0"/>