Tag Archives: Wireless Networking

Running Land Elevation Surveys With Google Earth

Background Information

Living in a rural area, I am often tasked with finding ways to connect remote sites to the Internet in places where cable and DSL are not available.  In these situations, the best alternative is usually the local wireless Internet service provider (WISP).

Many of these providers utilize point-to-point (PTP) and point-to-multipoint (PTMP) wireless connections running on non-licensed frequencies (900MHz, 2.4GHz, 5GHz, and others) to provide service to these types of hard to reach locations.

These connections work best with a line of sight (LOS) between your location and your ISP tower site.

From the ISP standpoint, determining whether an installation is viable usually comes down to visiting the site and trying to establish a connection, but running a few elevation surveys can help determine whether land barriers may have  a strong probability of obstructing the signal.

ISPs purchase expensive software tools to conduct these surveys, but a lot of it can be done with a reasonable amount of accuracy in Google Earth!

This tutorial will describe the basic steps needed to generate an elevation survey in Google’s free Google Earth desktop software.


1. Download and Install Google Earth.
At the time of this writing, Google Earth can be obtained here.

2. Locate Your Sites
Find the desired install site and the potential tower sites on Google Earth.  You can search by address, GPS coordinates (latitude & longitude), or by simply scrolling around the view.

3. Go to the “Add” menu, and click “Path”.
This will open the path editor, and turn your mouse into a tool to create path points.



4. Locate your first site, and click once to create a path point.
This will appear on your screen as a blue dot.



5. Locate your second site, and repeat the procedure, clicking on the site to make a path point.
This will appear on your screen as a second blue dot, and will create a white line which is your path.



6. Name the path.
Call it something other than “Untitled Path” to describe what the path is.  (eg. Tower Site A to Customer Site B).



7. Right click the path, and click “Show Elevation Profile”.
This will open the elevation profile view.





8. Expand on this, if you like.

You can create as many paths as you choose, name them accordingly, and even organize them into folders.  You can save Google Earth project files, which can be sent to customers, others at your organization, or anyone who suits your needs.

Keep in mind that the elevation profile is ground level elevation, so you will need to add heights of towers and buildings at either side to make the profile useful.

Also keep in mind that the elevation profile doesn’t know about trees and buildings in the area, so these will need to be factored in as well when determining the viability of a wireless signal.

All in all, this is a guideline and the results are not guaranteed to be useful every time, but can be a helpful tool for the WISP arsenal!

Affordable Wireless Bridge with Unlicensed Frequencies

I am a big advocate of not using wireless whenever possible for many reasons; security, interference, reliability, scale-ability, etc.  However the alternative can be extremely pricey, and just out of the question.  Our work has a building about 1400 Ft away from our primary building.  Its current network usage is nonexistent and although some feel our usage will be minimal.  I believe once we have Internet access out there we will see a much larger demand.  I am one who believes in doing it right the first time so it doesn’t have to be done again. Overbuilding is the key for longevity.  I am a big fan of Cisco equipment but in this build-out we will not be using Cisco.  They do offer some enterprise grade bridges but their cost is a little out of our budget on this project.

I played around with how to get the most amount of throughput on this, considered building two Linux boxes with directional antenna’s, priced out equipment, and came the conclusion that if we wanted a reliable connection we should go with equipment designed for what we are trying to do.  Kirk referred me to Ubiquiti We ended up purchasing the Ubiquiti Powerbridge M5 for $250 a radio (or $500 a pair).  This provides a 100Mb link on the 5.8 GHz spectrum which provides 23 non-overlapping channels compared to 2.4 GHz which only has 3.  These specific antennas are also ISP/carrier grade with a supposed distance of 20 kilometer range (don’t worry we turn the transmit power down 😛 ).

Once they arrived I went back to maintenance and grabbed some black pipe and a some scrap 3/4 In plywood.  In no time I whipped together a quick stand for testing.  I wanted something heavy on the bottom, the right size to screw into rafters when we finalized our testing, and cheap.  I also wanted to design it so I could set it on my counter top and not have to worry about scratching it up.  I was happy with the results, and the price… FREE

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We did some testing and found what we had predicted.  These antennas were WAY OVERKILL when it comes to range and current needed throughput… and that means that they were perfect!

They come with a built in spectrum analyzer to detect interference.  Due to our location we did not have any issues with that.  Kirk or I will post some more on the ubiquiti spectrum analyzer software at a later time.  My only complaint with that software is that it only runs on windows… and Linux is my primary OS…

Screenshot-[Concession-Bridge-MCHS] - Main - Chromium

Here is a screenshot of our current setup.  SSID, MAC Addresses, IP’s are all blacked out for obvious reasons.  This is the current link seen below.  This link is about 1400 feet.

Screenshot-Google Earth

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2012-10-12 15.15.13-scaled

These are outdoor rated antennas however I feel much safer having them under the protective roof.  I know that under an asphalt roof such as this that we will have greater signal loss, that partially why we purchased the antennas we did, to help compensate for that.

Since we have done this we are now streaming video games live to the Internet.  Our usage will be growing more and more with the quality of the video being sent to the Internet.  More and more people will want access, which is why we went with something like this rather than a 54Mb 802.11g connection.

The cost to pull this off with Cisco Aironet devises would have easily been closer to 3 times the cost.  We get a Cisco AP for about $600.  We would need 2 AP’s, plus cables, plus antennas.  We pulled this off at about $500, with a faster link.  Reliability will be determined later.  Currently we have been up for 60 days without problems.

With the success of this link and demand growing to all edges of our sports fields, we plan on building a redundant wireless network of our outbuildings for a minimal cost.

Screenshot-Google Earth-1

We will be putting Cisco AP’s out there to provide edge security/connectivity.

And just because they are rated for 20 kilometer does not mean you can shoot them through trees….  I couldn’t get them do go .5 mile through some trees.

NOTE:  Awesome Android app to help aim this equipment is “true bearing”.  With my minimal experience with some of the longer range equipment this could be very helpful IMHO.