[mapserver-users] Asking for guidelines about a project
Saka Royban
sakaroyban at yahoo.com
Mon Jun 20 02:10:01 EDT 2011
I don't know how to express my thanks to your helpful answer and Brent Fraser,
as well.
specially, i wasn't careful about using views in this application.
>>You don't need a table per vehicle, as all share the same columns, you just
>>need to have a vehicle id >>column to be able to select the required vehicle
>>from the table.
I didn't get what ur meaning. No table per vehicle? while i have to store every
point with its time, so it means 1 record for each point. (Can i have an array
of time in one cell? if so, it means i have a line of points in one cell, and
corresponding array of times in another cell)
>>Do you want a fixed map extent & just show vehicles in that region?
>>Do you want to have the map automatically zoom to an extent covering all
>>currently displayed vehicles?
>>Do you want the map to automatically recenter on a vehicle point as the point
>>nears an edge of the map?
Of course, user selects some vehicles, and if not in current displayed region,
map automatically changes the displayed extent.
Around recentering map when a vehicle reaches map edges, I think (if i'm wrong
Plz correct me) it would be done via Openlayers with some scripting. As it knows
current extent and new position of vehicles, it is possible computing whether
vehicle reaches edge or not.
Best Regards
Saka
________________________________
From: Brent Wood <pcreso at yahoo.com>
To: MapServer <mapserver-users at lists.osgeo.org>; Saka Royban
<sakaroyban at yahoo.com>
Sent: Sat, June 18, 2011 3:08:47 AM
Subject: Re: [mapserver-users] Asking for guidelines about a project
Given how these sorts of things tend to grow, it may also be worth planning for
a system to store the vehicle/points/times, as well as maintain the "live" table
of vehicle positions.
In fact the table of live positions can simply be a view on the historic table
providing the current situation instead of a physical table.
>From this you can automatically generate hourly or daily tracklines (linestrings
made up from the points within an interval ordered by time) which can also be
made available by mapserver, via an interface allowing users to select vehicles
& start/end times to show where they have been as well as where they are, or
where were they at a specified time.
With respect to automatic on screen map updates, it can get complicated:
Do you want a fixed map extent & just show vehicles in that region?
Do you want to have the map automatically zoom to an extent covering all
currently displayed vehicles?
Do you want the map to automatically recenter on a vehicle point as the point
nears an edge of the map?
A fixed extent is relatively easy, & can be done with a just mapfile & HTML
(have the web page retrieve the map automatically as a URL via WMS as often as
desired)
You don't need a table per vehicle, as all share the same columns, you just need
to have a vehicle id column to be able to select the required vehicle from the
table.
More powerful & flexible approaches are more complicated, but can be done. It
very much depends on what you want to do.
Cheers,
Brent Wood
--- On Sat, 6/18/11, Saka Royban <sakaroyban at yahoo.com> wrote:
>From: Saka Royban <sakaroyban at yahoo.com>
>Subject: Re: [mapserver-users] Asking for guidelines about a project
>To: "MapServer" <mapserver-users at lists.osgeo.org>
>Date: Saturday, June 18, 2011, 4:56 AM
>
>
>Thanks for ur answer and also Josh's answer.
>In fact, i should be able to display path of vehicles (usually more than 1
>vehicle in display area) and also be able to save points passed by vehicles and
>time of passing (for some queries). Cause of that, i thought maybe i need one
>table per vehicle.
>Do u think any more idea?
>
>Best Regards
>
>
>
>
________________________________
From: Brent Fraser <bfraser at geoanalytic.com>
>To: Saka Royban <sakaroyban at yahoo.com>
>Cc: MapServer <mapserver-users at lists.osgeo.org>
>Sent: Fri, June 17, 2011 7:49:20 PM
>Subject: Re: [mapserver-users] Asking for guidelines about a project
>
> The database schema depends on what you want to do with the data (display
>current position? A track of historical positions?), and how much data you
>expect (how may objects will be tracked? how often will they report?).
>
>A simple schema would have one table (e.g. "vehicles"), with one row per
>tracked object
>
>Table: Vehicles
>
>ID: Name: Position: Status: UpdateTime:
>1 My Car point(51,-115) active 2011-06-16 10:23:54+02
>2 Another Car point(52,-116) inactive 2010-05-15 11:13:12+02
>
>With this schema, when a new position arrives for "My Car", an update
>statement is issued to change the row's Position and UpdateTime (and
>possibly Status).
>
> The table is treated as a PostGIS point layer by mapserver.
>
> In my implementations, the position data was updated every 30 to 60
>minutes (they were ships and construction vehicles), so there was no need to
>ask mapserver to regenerate a graphic every second; an updated map was shown
>whenever a user did a pan or zoom. You may be able to configure OpenLayers
>to do a CGI request to mapserver every few seconds, but I've never done
>that.
>
>
>Best Regards,
>Brent Fraser
>On 6/16/2011 11:52 PM, Saka Royban wrote:
>Thanks a lot brent
>>I checked provided link and i;m gonna give it a try.
>>About ur helpful advices, i'm confused about how to save data in
>>PostGIS? with what schema?
>>
>>I mean i have to keep track of each paced point by moving objects.
>>Should i record each point as a record, so it means one table per
>>moving object ?
>>Also for displaying these varaiant data, there should some sort of
>>plan. I don't think i'm able to say to MapServer CGI at each second
>>connect to PostGIS and read the new data, then i have to use
>>MapScript. Am i right? (Can this process be done via OpenLayers?)
>>
>>Best Regards
>>
>>
>>
>>
________________________________
From: Brent Fraser <bfraser at geoanalytic.com>
>>To: Saka Royban <sakaroyban at yahoo.com>
>>Cc: MapServer <mapserver-users at lists.osgeo.org>
>>Sent: Tue, June 14, 2011 7:14:08 PM
>>Subject: Re: [mapserver-users] Asking for guidelines about a
>>project
>>
>> Saka,
>>
>> I've had good success using PostGIS for data storage in
>>implementing tracking systems. While you'll need to create your own
>>code for updating the positions in the database, mapserver can read
>>points from PostGIS and can render the points into a map image for
>>use with the OpenLayers client.
>>
>> There are other solutions too, like OpenGTS
>>(http://opengts.sourceforge.net/index.html)
>>
>>Best Regards,
>>Brent Fraser
>>On 6/14/2011 12:08 AM, Saka Royban wrote:
>>Hi all.
>>>Strictly Speaking, i have a project that i should display some
>>>moving objects on a map via browser.
>>>Generally, i don't know how to start? i mean how should i save
>>>these time-based objects in DB and how to retrieve and display
>>>them via Mapserver? where should i use client side scripting
>>>like OpneLayers?
>>>Any help woudbe greatly appreciated.
>>>
>>>Thanks in advance
>>>
>>>
>>>_______________________________________________
>>>mapserver-users mailing list
>>>mapserver-users at lists.osgeo.org
>>>http://lists.osgeo.org/mailman/listinfo/mapserver-users
>>>
>>
>>_______________________________________________
>>mapserver-users mailing list
>>mapserver-users at lists.osgeo.org
>>http://lists.osgeo.org/mailman/listinfo/mapserver-users
>>
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