Basic Terrain Plot, GPS & CSA

Basic Terrain Plot, GPS & CSA

A question emailed to me recently raised a useful point, which I thought would be useful to mention. By using a GPS receiver to trace the route along which test mesaurements are taken in a geographical area, would that reduce the need for terrain and clutter maps? The answer is absolutely not. Given the nature and purpose of a GPS receiver it does not and could not replace terrain and clutter maps. The purpose of the latter have an entirely different function to perform for cell site analysis (CSA) and evidence.

Below is an example of a basic terrain plot. I should point out there are many different versions that can be produced, but the one below will do for the purposes of this blog discussion. 

PRIMER - how to read the plot
The basic plot incorporates the following. Mast location (eg postcode, NGR etc), height above ground level of the antennas (trx) on the Mast, azimuth and a target reference location (eg postcode, NGR etc) where an incident is alleged to have taken place. The raw geo data can be obtained from national sources (eg Ordnance Survey or equivalent in other countries). The TERRAIN path profile has been mapped between those two locations in the plot below. The GREEN LINE represents the linear radio path between both reference locations. The RED LINE represents the TERRAIN between both locations. The BLACK ELLIPSOIDS identify obstructions in the line of the radio path. The BLACK LINE represents GSM "maximum acceptable boundary" (35 km).

The basic terrain plot should be prepared prior to conducting any site surveys, intended radio test measurements, etc. Importantly, this rules out the use of a GPS receiver replacing terrain and clutter maps because:

(a) the plot is produced prior to a site visit, so no e.g. GPS waypoints can be logged at this early stage; and
(b) the plot identifies aspects on the terrain path that need to be known; a GPS receiver can not provide such important information;      
(c) the plot also provides an advanced warning of potential locations where testing maybe needed and where a GPS receiver could be used to mark particular waypoints. Three examples from the plot above for waypoints (i) the small ellipsoid identifies the possibility of radio path interference such as potential attenuation, diffraction, reflection, shadowing, etc (ii) the large ellipsoid suggests blocking of the radio path with coverage being directed into the earth's surface and (iii) the target location is 48km distance from the Mast, thus beyond the maximum acceptable boundary. 

There is a considerable body of material and further discussion I could add about information and inferences about terrain plots (which is covered in the cell site analysis (CSA) course material), but I do not wish to give the impression, nor do I have the intention, of building a case against the use of GPS receivers. A GPS receiver is not a redundant tool. It is, though, only one very useful tool of many useful tools that are needed for cell site analysis (CSA). GPS should not be considered the tool that is capable of replacing other knowledge-based sources or test information gathering tools. The latter are as equally required for cell site analysis, and, in some instances, even more so.

Cell Site Analysis (CSA) Images Part 2

Cell Site Analysis (CSA) Images Part 2
.

It may interest those reading the discussions that I post that Cell Site Analysis (CSA) results from terrain and clutter analysis and radio test measurements can be defined in many different ways that can demonstrate particular elements of importance to a case.
.

Image 5

.
First we need to model (Image 5) the landscape that represents the geographical area and natural and manmade phenomenon in the surrounding area. In this case the scene of crime is close to a crossroads in the middle of small urban town.
.
For the sake of comfort, juries rarely understand radio coverage that is verbally discussed but respond much better to discussion revolving around a visual aid presentation.
.

Image 6

.
In this particular case I want to show the jury that two microcells* were used and each microcell first needs to be defined (Image 6) to the jury so they have it clearly in their minds the origin and direction of the radio coverage that forms part of the discussion.
.
In the first posting below (Cell Site Analysis (CSA) Images) coverage maps were shown defining large cell/macrocell coverage. Here, it is possible to refine and finesse coverage to a specific area with microcell coverage. Importantly, it is a really good idea to make sure the first image the jury sees represents the first radio coverage that a particular mobile phone has used that you want to talk about.
.

Image 7

.

The second microcell coverage (Image 7) should also be defined and distinguished. It's always best to remember with microcell coverage radio path is shaped in the same way as the High Street. Microcells don't go around corners.

.

Image 8

.

Finally the culmination of the presentation defines how the coverage from both microcells blend (Image 8 ) at particular points along the radio path.
.
*Remember that mobile telephones need to be encouraged to use microcell coverage and the microcell location, coverage boundary, speed at which a mobile phone is moving and cell reselection cause system challenges that required the use of a new criterion that was introduced into the GSM Phase 2 Standards in 1996. Do you know what that criterion is called and how it works?
.

Lastly, having mentioned microcell and large cell, the image below (Image 9) represents a visual indication about very important technical aspects concerning radio coverage and the layers depicted are often referred to in evidence. Indeed, if you care to read some of the Mobile Telephone Case Law you can find Appeal Courts referring to the importance of comprehending how far coverage extends.
.

Image 9

Cell Site Analysis (CSA) Images

Cell Site Analysis (CSA) Images
.
Cell Site Analysis (CSA) has had a good deal of airing recently here on the forum, so I thought you might like to see images from the work that I get involved.
.

Image 1

.
Image 1 is one slide from the training course material to introduce students to CSA when starting out discussing radio test measurements. It should be noted that this image represents less than 1% of all data acquired during radio test measurements.
.

Image 2

.

I thought it would be useful to include this Terrain and Clutter Map (Image 2) as I use this software to assist me in complex cases. Terrain and Clutter are discussed during training and as it was a topic of the discussion about UK Criminal Evidence Delays I thought it would be helpful to let forum members see that I am not referring to theoretical matters, terrain and clutter analysis actually takes place.

.

Image 3

.

It is essential to understand, when conducting radio test measurements, that just because radio signals can travel some distance from a particular Mast (Image 3) that coverage should not be dismissed or excluded. Operators set threshold limits, hard limits and boundary limits. It does not follow that just because a mobile is in the Green area shown in the Single Cell Prediction Map that the mobile will be excluded from using that coverage.

.

Do you remember the discussion that I put up here CSA: Mobile Phones and Fringe Coverage?:
.

Image 4

.

Best serving coverage is often posed as the deal-clincher to suggest the mobile phone was most likely or consistent with being at a particular location. There can be numerous points that could (and I say 'could' advisedly) point to best server coverage being used but rarely does it come up in evidence because the radio content in evidence rarely gets disclosed these days.

.

It is possible with best serving coverage that it can induce a negative outcome that may prevent calls taking place, so it is always important to see the other side of the coin, so to speak:
.
GSM Radio Test Measurements Non-Dominance
GSM Radio Test Measurements
.

I hope the above provides a further illustration of how smart and intelligent a science Cell Site Analysis really is and that by not applying it properly and dumbing down this art of this forensic science:

.

- is not only a great loss to the law of evidence

- it reduces the examiner's/expert's knowledge and understanding about the subject with which they are dealing - mobile telephone evidence.

Cell Site Analysis (CSA) Images Part 2

Cell Site Analysis (CSA) Images Part 2
.

It may interest those reading the discussions that I post that Cell Site Analysis (CSA) results from terrain and clutter analysis and radio test measurements can be defined in many different ways that can demonstrate particular elements of importance to a case.
.

Image 5

.
First we need to model (Image 5) the landscape that represents the geographical area and natural and manmade phenomenon in the surrounding area. In this case the scene of crime is close to a crossroads in the middle of small urban town.
.
For the sake of comfort, juries rarely understand radio coverage that is verbally discussed but respond much better to discussion revolving around a visual aid presentation.
.

Image 6

.
In this particular case I want to show the jury that two microcells* were used and each microcell first needs to be defined (Image 6) to the jury so they have it clearly in their minds the origin and direction of the radio coverage that forms part of the discussion.
.
In the first posting below (Cell Site Analysis (CSA) Images) coverage maps were shown defining large cell/macrocell coverage. Here, it is possible to refine and finesse coverage to a specific area with microcell coverage. Importantly, it is a really good idea to make sure the first image the jury sees represents the first radio coverage that a particular mobile phone has used that you want to talk about.
.

Image 7

.

The second microcell coverage (Image 7) should also be defined and distinguished. It's always best to remember with microcell coverage radio path is shaped in the same way as the High Street. Microcells don't go around corners.

.

Image 8

.

Finally the culmination of the presentation defines how the coverage from both microcells blend (Image 8 ) at particular points along the radio path.
.
*Remember that mobile telephones need to be encouraged to use microcell coverage and the microcell location, coverage boundary, speed at which a mobile phone is moving and cell reselection cause system challenges that required the use of a new criterion that was introduced into the GSM Phase 2 Standards in 1996. Do you know what that criterion is called and how it works?
.

Lastly, having mentioned microcell and large cell, the image below (Image 9) represents a visual indication about very important technical aspects concerning radio coverage and the layers depicted are often referred to in evidence. Indeed, if you care to read some of the Mobile Telephone Case Law you can find Appeal Courts referring to the importance of comprehending how far coverage extends.
.

Image 9

More on Cell Site Analysis: http://cellsiteanalysis.blogspot.com

Cell Site Analysis (CSA) Images

Cell Site Analysis (CSA) Images
.
Cell Site Analysis (CSA) has had a good deal of airing recently here on the forum, so I thought you might like to see images from the work that I get involved.
.

Image 1

.
Image 1 is one slide from the training course material to introduce students to CSA when starting out discussing radio test measurements. It should be noted that this image represents less than 1% of all data acquired during radio test measurements.
.

Image 2

.

I thought it would be useful to include this Terrain and Clutter Map (Image 2) as I use this software to assist me in complex cases. Terrain and Clutter are discussed during training and as it was a topic of the discussion about UK Criminal Evidence Delays I thought it would be helpful to let forum members see that I am not referring to theoretical matters, terrain and clutter analysis actually takes place.

.

UK Criminal Evidence Delays: http://www.forensicfocus.com/index.php?name=Forums&file=viewtopic&t=3961

.

Image 3

.

It is essential to understand, when conducting radio test measurements, that just because radio signals can travel some distance from a particular Mast (Image 3) that coverage should not be dismissed or excluded. Operators set threshold limits, hard limits and boundary limits. It does not follow that just because a mobile is in the Green area shown in the Single Cell Prediction Map that the mobile will be excluded from using that coverage.

.

Do you remember the discussion that I put up here about fringe coverage?: http://trewmte.blogspot.com/2008/11/mobile-phones-and-fringe-coverage.html
.

Image 4

.

Best serving coverage is often posed as the deal-clincher to suggest the mobile phone was most likely or consistent with being at a particular location. There can be numerous points that could (and I say 'could' advisedly) point to best server coverage being used but rarely does it come up in evidence because the radio content in evidence rarely gets disclosed these days.

.

It is possible with best serving coverage that it can induce a negative outcome that may prevent calls taking place, so it is always important to see the other side of the coin, so to speak:
.
- http://trewmte.blogspot.com/2007/02/gsm-radio-test-measurements-non.html
- http://trewmte.blogspot.com/2007/01/gsm-radio-test-measurements.html
.

I hope the above provides a further illustration of how smart and intelligent a science Cell Site Analysis really is and that by not applying it properly and dumbing down this art of this forensic science:

.

- is not only a great loss to the law of evidence

- it reduces the examiner's/expert's knowledge and understanding about the subject with which they are dealing - mobile telephone evidence.

More on Cell Site Analysis: http://cellsiteanalysis.blogspot.com