Annotating Digital Charts

I’ve said before, I’m not a fan of massively featured navigation software.  It has steep and multiple learning curves, it gobbles computer resources and it pushes one toward vendor lock-in. All bad juju. One area where I find such software lets me down in particular is when I want to draw on a chart. Not plotting mind you, but notes and graphics which add to the information value of the chart.

I use Oziexplorer charting software. There’s no learning curve, it’s computer friendly, and it accepts input from my AIS which acts as a GPS multiplexer — everything that can come from a GPS can be delivered via a single cable. I use a very burned-in IBM X40 running Windows 7. Since this laptop is for nothing but Nav, augmenting it with 16 extra GB via an SDHC card makes it more than roomy enough. SO WHAT? Oziexplorer (and some others out there) allows me to use JPGs with geospatial references as charts.* I save the added information as a graphic layer in an open source editor (Gimp), so underlying charts can be swapped out as new ones are issued. Three examples of where I have done this are:

Converted BSB** charts to JPGs and emphasized or color highlighted obscure features (or important features lost when charts scale to 1:1,200,000 — Added point of no return circles — added range rings to key ports from offshore — highlighted and annotated shipping separation schemes based on AIS plots collected over time. Note the color change to remind me I’m not on an unaltered NOS chart

Used Gulf Stream flow charts as moving maps to get a better sense of my boat’s location in the flow and what that flow might look like the next day. 

Used layered GRIB charts as charts to get a sense of our movement through the wind field.
Can one do these kinds of things with $700-$1200 navigation suites at the flick of a virtual button? Yep. Can I do them with a tad of work using open/freeware and a $90 charting program, Yep, and in the bargain, I develop a mental imprint from handling the information that I would not get from just looking at it.

When I was actively flying an airplane with one radio and enough instruments to get oneself upright (if there was enough altitude) I always took my chart and marked every runway within gliding distance of my planned altitude and flight-path from beginning to end. This is the same kind of thinking.

*Always verify scanned/georeferenced charts for lat/lon. Some Nav software use imperfect algorithms, and I’ve seen such charts off by as much as 4 miles at 1:1,200,000.

**BSB to JPG conversion software can be found for free at SourceForge


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