Many nautical charts have elevation units in feet and depths in units other than meters, such as fathoms and fractions, fathoms and feet, and feet. When this occurs, use the units shown on the chart to collect your elevation and depth attributes. What you see on the chart is what you enter as your value when attributing a feature. This makes quality control more efficient and accurate.
Converting units
Once a chart is ready to be edgematched or converted to VPF, all the units should be converted to meters. This allows accurate edgematching.
Once you convert your units, you are not allowed to convert those features again. With the Units Conversion tool, you can convert based on your Dqyarea extent or a selected set of features.
Original unit values are moved to a field called orig_<item> in the feature table. You can label this field in ArcMap for visual quality control purposes. All the orig_<item> fields default to -99999. If you import your data with the VPF Importer, they default to 0. Once converted, the Units Conversion tool will not run on features with orig_<item> not equal to -99999 or 0.
| Feature class | Elevation fields | Depth fields |
|---|---|---|
AqueductL | OHC | |
BridgeA | MVC,OHC,SHC | |
BridgeL | MVC,OHC,SHC | |
BuoybcnP | EOL | |
CanalA | WID | HDP |
CanalL | WID | |
DangerA | HDP | |
DangerP | HDP | |
HazardA | HDP | |
HazardP | HDH | HDP |
Hydarea | CVH,CVL | |
Hydline | CRV | |
IndustP | HGT,ZV2 | |
IndustA | ZV2 | |
LightsP | EOL | |
MaritimA | WID | HDP |
MaritimL | WID | HDP |
MisciwyA | WID | |
PipelinL | DEP,HSB,OHC | |
PowerL | OHC | |
ReefA | HDH | HDP |
Relline | ZV2 | |
Relpoint | ZV2 | |
RouteA | HDP | |
RouteL | HDP | |
RuinsA | HDH, HGT | HDP |
RuinsP | HDH | HDP |
SnowiceP | HGT | |
SoundP | HDH | HDP |
SepartnA | WID | |
SepartnL | WID | |
SweptA | HDP | |
SweptL | HDP | |
TunnelL | HDP |