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Andy_P
Pocket GPS Moderator
Joined: Jun 04, 2005
Posts: 19991
Location: West and Southwest London
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 Posted: Sun Apr 11, 2010 7:19 pm Post subject: |
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...........
Last edited by Andy_P on Sun Apr 11, 2010 7:25 pm; edited 1 time in total |
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Andy_P
Pocket GPS Moderator
Joined: Jun 04, 2005
Posts: 19991
Location: West and Southwest London
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| Posted: Sun Apr 11, 2010 7:21 pm Post subject: Re: WARNING - TomTom's fuel POIs can disrupt the Camera warn |
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| M8TJT wrote: | | Even worse, they must already have the gash code do the sums on the fly in the satnav |
So it's being yet another bit of pointless code SLOWING DOWN the core application!  |
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AliOnHols
Pocket GPS Verifier
Joined: Oct 15, 2008
Posts: 1942
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| Posted: Sun Apr 11, 2010 7:31 pm Post subject: |
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Post deleted. Sorry M8TJT, even fewer clues!
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Garmin Nuvi 2599
Android with CamerAlert, OsmAnd+, Waze & TT Europe.
TomTom GO 730, GO 930, GO 940 & Rider2.
SatMap Active 10 & 20.
Last edited by AliOnHols on Sun Apr 11, 2010 7:45 pm; edited 1 time in total |
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Andy_P
Pocket GPS Moderator
Joined: Jun 04, 2005
Posts: 19991
Location: West and Southwest London
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| Posted: Sun Apr 11, 2010 7:39 pm Post subject: |
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Whoops, on reflection, I moved that post of mine over to a quieter part of the forum. No quick enough, obviously!  |
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M8TJT
The Other Tired Old Man
Joined: Apr 04, 2006
Posts: 10118
Location: Bexhill, South Sussex, UK
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| Posted: Sun Apr 11, 2010 7:40 pm Post subject: |
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I wish I knew what you are all talking about  |
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Andy_P
Pocket GPS Moderator
Joined: Jun 04, 2005
Posts: 19991
Location: West and Southwest London
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| Posted: Sun Apr 11, 2010 9:39 pm Post subject: |
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Don't worry, nothing important. Just me going off-topic again.  |
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BMW330
Pocket GPS Verifier
Joined: May 20, 2006
Posts: 389
Location: Sydney, Australia
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| Posted: Mon Apr 12, 2010 10:17 am Post subject: |
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| PaulB2005 wrote: | | Please don't use asterisks to circumvent the auto censor.... |
Sorry, I wasn't aware of the existence of an auto-censor - I was censoring my own comment. |
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BMW330
Pocket GPS Verifier
Joined: May 20, 2006
Posts: 389
Location: Sydney, Australia
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| Posted: Mon Apr 12, 2010 10:28 am Post subject: Re: WARNING - TomTom's fuel POIs can disrupt the Camera warn |
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| Andy_P wrote: | | M8TJT wrote: | | Even worse, they must already have the gash code do the sums on the fly in the satnav |
So it's being yet another bit of pointless code SLOWING DOWN the core application! |
Yip, and it gets better. I've noticed that many of the websites that provide TomTom POI in the form of .ov2 files don't bother to index these downloads (NB: PGPSW is not one of these rogue sites!) - so if TT wants to know what POI are within x distance, it has to read and check every individual POI record in the whole ov2 file - imagine if that file has tens of thousands of entries in it, and if you have a number of them. An indexed ov2 file on the other hand can typically be drilled into to find the records of interest very, very efficiently with about 1-5 read operations. |
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Andy_P
Pocket GPS Moderator
Joined: Jun 04, 2005
Posts: 19991
Location: West and Southwest London
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| Posted: Mon Apr 12, 2010 8:14 pm Post subject: Re: WARNING - TomTom's fuel POIs can disrupt the Camera warn |
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| BMW330 wrote: | I've noticed that many of the websites that provide TomTom POI in the form of .ov2 files don't bother to index these downloads
- so if TT wants to know what POI are within x distance, it has to read and check every individual POI record in the whole ov2 file
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An indexed ov2 file on the other hand can typically be drilled into to find the records of interest very, very efficiently |
Interesting..... I didn't know about that.
What form does this indexing take then? I thought an POI file was just a simple list of placenames, Lat/Long coordinates and an optional phone number.
| BMW330 wrote: | | (NB: PGPSW is not one of these rogue sites!) |
So what do places like PGPSW do differently? |
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Darren
Frequent Visitor
Joined: 11/07/2002 14:36:40
Posts: 23848
Location: Hampshire, UK
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| Posted: Mon Apr 12, 2010 10:25 pm Post subject: Re: WARNING - TomTom's fuel POIs can disrupt the Camera warn |
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| Andy_P wrote: | | So what do places like PGPSW do differently? |
We index our files
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Andy_P
Pocket GPS Moderator
Joined: Jun 04, 2005
Posts: 19991
Location: West and Southwest London
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| Posted: Mon Apr 12, 2010 10:54 pm Post subject: |
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So he said, but what does it involve?
Is it a header to the file or something in each record? Because all I know is each individual record uses (using the easier to read .csv version for clarity) either simple 3 column records: longitude, latitude, name
or 4 column records: longitude, latitude, name, comment
such as (some examples I stole of the net)
-110.12345,44.98765,"ACME Shoe Store","Phone: 555-829-8293"
-110.12332,44.98622,"Ace Lock Smith","24 hour service"
-110.12131,44.91422,"Public Restroom",""
-110.11932,44.95662,"Golden Kites","123 Main Street"
-110.11310,44.94222,"Public Restroom",""
What's the index do and where does it go? I'm obviously not asking Google the right questions |
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pcaouolte
Frequent Visitor
Joined: Dec 27, 2006
Posts: 998
Location: South Lincs, UK.
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| Posted: Tue Apr 13, 2010 1:05 pm Post subject: |
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Andy,
From memory the ov2 file can contain type 1 records that define a rectangle and type 2 records that contain details of the POI's within that rectangle. There are also other record types that contain POI data but in a compressed form.
If the ov2 file contains only type 2 records the tomtom will need to search the whole file to find a POI.
If the ov2 file is "indexed" with type 1 records then the tomtom can know which rectangle is currently displayed on screen and find all POI's within the "current" rectangle (and adjacent rectangles) without searching the whole file.
To clarify (?) the ov2 file can contain:
Type 1 record: Defines area covered by whole map
Type 1 record: Defines a smaller area within map
Type 1 record: Defines yet smaller area
.... eventually
Type 1 record: Defines very small area
Then (perhaps 10) Type 2 records: Define POI's within very small area
Type 1 record: Defines another very small area
More Type 2 records within that small area.
I have more precise details of the workings of this at home if you want them.
Does that help?
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Paul |
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Andy_P
Pocket GPS Moderator
Joined: Jun 04, 2005
Posts: 19991
Location: West and Southwest London
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| Posted: Tue Apr 13, 2010 2:42 pm Post subject: |
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| pcaouolte wrote: |
Does that help? |
It certainly does, thanks 
So is indexing only available for .ov2 format files, or is there an equivalent for Garmin/csv and others?
And what sort of software would you need to *do* the indexing? The usual POIEdit/Tyre et.c progs don't seem to have that sort of functionality. |
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pcaouolte
Frequent Visitor
Joined: Dec 27, 2006
Posts: 998
Location: South Lincs, UK.
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| Posted: Wed Apr 14, 2010 1:05 pm Post subject: |
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Sorry Andy, I only have a tomtom so I haven't any info on Garmin devices.
The better quality pieces of software that create ov2 files automatically put the indexing type 1 records into the file without asking the user. I can't find any info on the POIEdit or Tyre web sites to say if they include the type 1 records or not but I would expect that they do.
To find out, you could create an ov2 file using POIEdit or Tyre and then examine the ov2 file with a hex editor. If the first byte in the file is hex 01 then the file is indexed. Any other value in the first byte and the file is not indexed. A short example of the first part of an indexed ov2 file downloaded from this site with the start of each type 1 record highlighted in red and the start of each type 2 record highlighted in blue is shown below:
01 4a 01 00 00 4c e2 ff ff f4 f5 4f 00 e7 d1 f9
ff 33 e4 4c 00 01 90 00 00 00 1a da fc ff f4 f5
4f 00 e7 d1 f9 ff 33 e4 4c 00 01 3c 00 00 00 1a
da fc ff 13 6d 4e 00 e7 d1 f9 ff 33 e4 4c 00 02
27 00 00 00 e8 d1 f9 ff 34 e4 4c 00 50 6c 79 6d
70 74 6f 6e 2c 20 44 65 6c 69 76 65 72 79 20 4f
66 66 69 63 65 00 01 3f 00 00 00 1a da fc ff f4
f5 4f 00 e7 d1 f9 ff 13 6d 4e 00 02 2a 00 00 00
73 d4 f9 ff f5 f5 4f 00 41 62 65 72 79 73 74 77
79 74 68 2c 20 44 65 6c 69 76 65 72 79 20 4f 66
66 69 63 65 00 01 a5 00 00 00 4c e2 ff ff f4 f5
4f 00 1a da fc ff 33 e4 4c 00 01 51 00 00 00 4c
e2 ff ff 13 6d 4e 00 1a da fc ff 33 e4 4c 00 .......
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