Re: [OpenMap Users] Discovering the minimum scale at which an RPF layer will show

From: Don Dietrick <>
Date: Mon, 7 Mar 2005 09:59:48 -0500

Hi Laura,

The code you have is exactly what you want to use. I guess I don't
understand the difference between asking for coverage for a point, and
your problem with having the bounding box in the query being too small.
  It seems like they would both provide the same answer.

Has the RpfLayer been added to the map? The RpfTocHandler doesn't read
the A.TOC file until it needs to display something, so it probably
wouldn't know anything until then.

- Don

On Mar 7, 2005, at 9:29 AM, Laura Paterson wrote:

> Hi Don,
> Thank you for your reply.
>> You can ask the RpfLayer for it's RpfCoverageProvider, and then ask it
>> for it's coverage over a specific area. Those coverages will tell you
>> what scale you need to view that data. The coverage will viewable at
>> that scale * or / by the scaleFactor of that value.
> Ok, I have tried that, but it doesn't quite do what I am looking for.
> Here
> is the code that I used:
> for (int i = 0; i < layers.length; i++) {
> if (layers[i] instanceof RpfLayer) {
> RpfLayer rpf = (RpfLayer)layers[i];
> RpfFrameProvider fProvider =
> rpf.getFrameProvider();
> Vector cvgs =
> fProvider.getCoverage((float)minLat, (float)minLon, (float)maxLat,
> (float)maxLon, (CADRG)proj);
> for (int j=0; j<cvgs.size(); j++) {
> RpfCoverageBox box =
> (RpfCoverageBox)cvgs.get(j);
> System.out.println(layers[i].getName()
> + "
> scale from coverage = "+box.scale);
> minScale = Math.min(minScale,
> box.scale);
> }
> }
> }
> Unfortunately there area never any coverages for this bounding box,
> because
> it covers such a small area...
> I tried replacing the Vecor cvgs line with : Vector cvgs =
> rpf.getCoverageBoxes(); However, this Vector is always empty.
> I guess what am looking for (ideally!) is to be able to specify a
> point,
> and ask at what scales will this point have rpf coverage. Is there
> anything
> in the API that can help me achive this?
> Thanks,
> Laura
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Don Dietrick,
BBN Technologies, Cambridge, MA

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Received on Mon Mar 07 2005 - 10:00:14 EST

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