Hi Matt,

When we developed this tool, the goal was to produce a “quiver plot”, which is a field of arrows pointing in the direction of flow, with lengths scaled to the magnitude of flow. It would be nice if ArcGIS supported that directly as a symbology option; for example, given point features, it could draw arrows with the direction and magnitude determined by two attributes of the points. But it does not have that capability, so we had to resort to a hack: the MGET tool creates a line feature class with the lines drawn in the direction of flow and with lengths proportional to the magnitude of the flow. The Scale Factor parameter of the tool is basically a multiplier to make the lines shorter or longer, to manage their appearance.

Instead, you would like the lines to all be the same length, regardless of the magnitude of the flow. You would then use the magnitude attribute to color them according to magnitude. That sounds like an interesting approach. Unfortunately the tool cannot currently do that because it always draws the lines proportionally to the magnitude.

I cannot think of an easy way to achieve the desired effect. It is possible to use map algebra to produce u and v rasters in which each cell has the same magnitude of flow, just a different direction. If you ran the MGET tool on those, you would get lines pointed in the direction of flow but that were all the same length. Unfortunately the magnitude attribute of those lines would be the same value, so you could not color the lines according to magnitude. Perhaps if you then computed magnitude in raster form using map algebra, then converted that raster to points, then did a spatial join of the points to the uniform-length lines… That is very complicated but seems possible.

Is producing maps of this kind an important capability? I might be able to modify the MGET tool to allow this as an option. It would have a checkbox or something that told it to generate lines of uniform length but still write the attributes indicating the true magnitude.

Best,

Jason

I am trying to figure out how to modify the symbolization of the vector lines developed from ocean current component rasters. I would like to modify the vector line symbology from line length representing magnitude, to defined or classified colors representing magnitude. In my attempt to do this I realized I do not understand how the lines are generated from the component rasters in the first place. I could not find clues in the tool code. What am I missing?

Thanks

Matt