Re: [OpenMap Users] Questions on how to use OpenMap as an applet which uses data from server

From: Don Dietrick <>
Date: Mon, 6 Jun 2005 09:57:57 -0400

Hi Mariusz,

On Jun 6, 2005, at 7:40 AM, Mariusz Chmielewski wrote:

> Using relative path isn't such a great idea becouse of the size of
> the RPF map (32 MB) would You suggest?? I have a problem putting
> such data into the JAR - i do not know if the JAVA VM will allow to
> execute such application.

Is your problem that you don't know if it will work? I would suggest
trying it to prove to yourself that it does.

> I am thinking of using Java Web Start but this does not solve my
> problem i do not want to put map data into my jar file of an applet
> is there a chance thath if i point to map in URL openMap layer will
> automaticly download it itself??

You can also reference a URL in the RPF path, but it will be slower.
If the data is in the jar, the user takes the download hit one time.
If the data is in the URL, each compressed frame will be downloaded
as needed.

> is there a chance that i could write some code as a servlet that
> loads a whole CADRG map and sends only little piec of it as a new
> CADRG map.

There is no CADRG 'map'. CADRG is made up of sub-frame images
(256x256 pixels) from frame files (6x6 subframes) that get put
together at runtime. If you use the URL approach, the frame files
will be downloaded to the client.

> Has anybody tried it??


> why the engine of open map is so slow while using the CADRG data.
> When i scroll 3 layer on my 2,2 GHz Pentium 4 512 RAM - i am
> waiting almost 5 seconds befor i can see anything.

What's your map scale, and what kind of maps are you using? It
sounds like you are zoomed out from the map scale of the charts you
are viewing, so you are probably reading quite a bit of data to
display. I/O takes time.

- Don

>> Hi Mariusz,
>> On May 27, 2005, at 8:50 AM, Mariusz Chmielewski wrote:
>>> Hi I am now experiencing some problems with teh open map as an
>>> applet. I written my own applet so it would be downloaded from
>>> the server and it contains openmap. But i ve got some issues that
>>> i cannot solve:
>>> 1. i am using the CADRG MAPS, those are the spatial data which
>>> requires large amount of memory about 2MB and the question is
>>> should i put the data into the jar file, or should i put the data
>>> on the server and download it or should i simply load the
>>> resources on the client. Ofcourse the 3 option is the worst
>>> becouse i do not want the spatial data to be accessable on the
>>> client maschine outside the applet. (additional info to the first
>>> option how to load a map using properties file from local applet
>>> resources??)
>> You can put the data in a jar file.
>>> 2. Concerning properties configuration (same as the map) where it
>>> should be placed inside jar and how to load it??
>> You would configure the RPFLayer to have a relative path to the
>> RPF directory in the jar file, from the root of the jar file.
>>> 3. Is there a chance that i could load only a part of CADRG map
>>> and the load the rest if neccessery?? so that i could minimize
>>> the size of used memory during the execution of the applet??
>> That's the way the layer works now. It only loads what it needs.
>> You can change the cache sizes so it holds onto less memory if you
>> need that.
>> - Don
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Received on Mon Jun 06 2005 - 09:59:33 EDT

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