Mapboard GIS


The topo­log­i­cal ca­pa­bil­i­ties of Map­board GIS in ac­tion

The topo­log­i­cal edit­ing ca­pa­bil­i­ties of Map­board GIS are a ma­jor step to­wards it­er­a­tive ge­o­logic map­ping. When topo­log­i­cal edit­ing is en­abled, unit de­f­i­n­i­tions snap to their en­clos­ing linework, al­low­ing the struc­ture of the map to emerge as map­pers fo­cus on cap­tur­ing data.

In Spa­tialite mode and Im­age mode, the on­board Spa­tialite en­gine is used to man­age topo­log­i­cal re­la­tion­ships. The ref­er­ence im­ple­men­taion of topo­log­i­cal edit­ing ca­pa­bil­i­ties is the Post­GIS Ge­o­logic Map topol­ogy solver op­er­at­ing in Teth­ered mode.

Spa­tialite sup­port for topol­ogy is slower and more bug-prone than the Post­GIS ref­er­ence im­ple­men­ta­tion. The un­der­ly­ing al­go­rithms will be im­proved over time. Please file is­sues as needed to doc­u­ment un­ex­pected be­hav­ior.

The Topol­ogy set­tings panel

In both modes, the Topol­ogy set­tings panel man­ages whether topo­log­i­cal edit­ing is ac­tive, and whether filled map faces are shown. Dur­ing topo­log­i­cal edit­ing, each change to the map re­sults in a re­build of the mod­i­fied area. The Post­GIS Ge­o­logic Map en­gine is good at find­ing the min­i­mum set of re­la­tion­ships to change, but the Spa­tialite back­end cur­rently uses a less ef­fi­cient al­go­rithm.

On­board topo­log­i­cal solv­ing is a com­plex, bat­tery-drain­ing al­go­rithm, and iPads have lim­ited sys­tem re­sources. Real-time topo­log­i­cal solv­ing should be turned off dur­ing in­ten­sive field use if sta­ble power avail­abil­ity is a con­cern.