HeyWhatsThat WISP
Fixed Wireless Analysis

Getting Started videos

Free (as in beer)

   wisp.heywhatsthat.com?user=free5

and you can save up to five towers in a browser cookie and export up to five towers to a CSV file. (The Save button is under the Towers tab.)

Trial Account

   wisp.heywhatsthat.com/signup.html

The trial account gives you five sessions for $1.

A session lasts twenty minutes. A session doesn't start until you click on the map to request a line-of-sight computation. (So you can work on your tower list, for example, without starting a session.)

You can use the trial sessions with any number of towers.

Accounts

• if you have 20 or fewer towers, you can buy more sessions for $1 per session (minimum purchase $10)

• if you have 100 or fewer towers, you can buy a subscription at $100 per month

• if you have more than 100 towers, please for pricing

Mobile Site for Subscribers

Line of Sight Computation

But please keep in mind that the profiles and viewsheds are certainly not definitive; e.g. if a customer is a bit outside the viewshed you still may be able to reach them.

If we're getting a lot of traffic, we may stop the demo from automatically requesting the computation, and instead require you to hit the Compute LOS button; the button will be bold in that case.

In the site list on the left there's a indication of LOS quality (+++ ++ + -). This is a measure of the maximum obstruction to the first Fresnel zone (the orange lozenges on the profile graphs).

	+++	80% or more of the zone is clear (we believe this is the standard RF criterion for a good link, but please let us know if you disagree)
	++	50% or more of the zone is clear (which means there's a clear line of sight)
	+	some of the zone is clear
	-	zone completely obstructed
		The + or - may be colored yellow; if so, the number that follows is the height above ground that you'll get a clear line of sight at the customer location
		if the column is blank for all the towers, either the computation hasn't finished (you'll see computing ... at the top of the page), or, as mentioned above, you have to hit the Compute LOS button

We don't know how these actually correspond to signal strength, and we're exploring other propagation models. We're open to suggestions for refining our approach.

Other caveats:

• We use SRTM elevation data, which is not always ground-level but sometimes rooftops and treetops, is not high resolution (particularly outside the US), and has many empty areas. It was developed by downward looking radar on the February 2000 Space Shuttle mission.

  The simplest way to check the quality of data in your area is to examine the contour lines you get when you hit the Contours button in the upper right-hand corner of the map.

Land Cover Data (trees)

• you will see an indication of trees on the profile images
• you can click the "Landcover" button at the top-right of the map to see landcover classes overlaid on the map

The landcover information is only a visual addition to the profiles; it is not currently taken into account in either the path quality computation (that determines the +++, ++, ... and the color of the towers) or the viewsheds.

In addition to the land cover data, we're looking at US tree canopy data from the same USGS source. The land cover database marks every 30m x 30m block by its type (forest, shrub, developed, ...), while the tree canopy database gives a percentage of tree cover for every block. If you would like to try it out, please get in touch.

Tower Data

• Notes
  You may want to use a controlled vocabulary in this field. We currently provide a hack where we build a button in the UI to enable or disable towers whose notes field match a regular expression. Or, you can give provide a regular expression as a URL parameter, eg.

      http://wisp.heywhatsthat.com?user=XXXX&notesgrep=active

  or

      http://wisp.heywhatsthat.com?user=XXXX&namegrep=NYC

  and you'll get a page showing only those towers with matching name or notes field.

• Viewshed colors
  Enter RGBA values. The A (the final two hex digits) is alpha transparency, ranging from 00 (opaque) to 7F (transparent).

• Antenna sectors
  You can specify antenna beamwidths for directional antennas. Check show sectors and you'll get a column where you can enter them. When you add sectors you'll get feedback on whether or not a customer falls within the sector or sectors you've specified: the plus signs + will be replaced by degree symbols ° if the customer is outside all the tower's sectors. But remember that the site is based on line of sight, not signal strength, so there is no concept of a signal fall-off as you approach the beam edge: you're either in the sector or you're not. In particular, if you're covering all 360 degrees through a combination of sectors, then entering sectors might not add anything to the analysis. But see below, where you can label and color the sectors and have them appear on the map.

  The syntax is

      center/beamwidth[,center/beamwidth...]

  For example, for an antenna pointed due west with a 100° horizontal beamwidth (so it covers 220° to 320°) the entry is

      270/100

  If the azimuths are magnetic (rather than true), preface the entry with an m. If you want to have several sectors on the same entry, separate them with commas. e.g.

      m270/100,90/100

  means two sectors with beamwidth 100°, one pointed towards magnetic west and the other magnetic east.

  You can specify vertical sectors by adding

      :vertical center/beamwidth

  to the string. So

      270/100:0/10

  is a sector facing west, ranging from azimuth 220° to 320°, with the beam limited to 5° above and below the horizon

      m270/100:0/10,90/100

  covers magnetic 220° to 320° with the same vertical restriction and magnetic 40° to 140° with no vertical restriction

      :0/10

  is omni-directional with the specified vertical beamwidth

  We can also enable your account to display the sectors on the map -- contact us to set it up -- and you can add colors and labels to the entries. You color a sector with #RGBA, where the color is the same RGBA format as the viewshed color (e.g. "202/90#FF00FF20"). But note that areas of overlap will only show one color, and not consistently the first or last listed.

  You add a name to a sector with @name, where the names can only be letters and numbers and underscores (_), and the underscores will be replaced with spaces on the map. Colors must precede name if you gave both.

  So here's an exmaple with two sectors, one minimal, the other showing all the options, using magnetic azimuths:

  m0/120,202/90:5/30#FF000020@alpha_123

  A second way to set colors for the sectors is by entering multiple colors in a tower's viewshed colors cell. Use a series of comma-separated values. For example, if the sectors are "90/100,270/100", then the viewshed color entry "ff000040" will color both sectors red, but "ff000040,00ff0040" will color the east-facing sector red and the westerly green.

• Ground elevation
  You can override the ground elevation (that we add to the tower height to get its height above sea level). If the radar signal used by the SRTM mission bounced back from the top of the tower — eg. if it's a really big tower — then the ground elevation recorded for that spot may include the tower height.

"Name   [v. 1.0]",Latitude,Longitude,"Tower height (ft agl)","Maximum range (miles)","Ground elevation (ft amsl)",Notes,"Viewshed color (RGBA)","Sectors (center/beamwidth)"
"Test tower",44.222857,-69.068648,20,5,777.6,,f1b0b020,

or Metric units:

"Name   [v. 1.0]",Latitude,Longitude,"Tower height (m agl)","Maximum range (km)","Ground elevation (m amsl)",Notes,"Viewshed color (RGBA)","Sectors (center/beamwidth)"
"Test tower",44.222857,-69.068648,6,8,237,,f0b0b020,

and add your own data. Be sure to include the row of headings when you prepare a CSV file to import.

If you want to build spreadsheets with your own data in them as well, leave a blank column (ie. the header row should have a blank column) between the data we require and your data; our import will ignore everything to the right of that blank column.

Things That May Not Be Obvious

• The viewsheds are computed using whatever elevation above ground you've set for the customer location, i.e. a spot on the map is colored if there's a clear line of sight from the tower to a point that many feet above ground at that spot. (This differs from the original behavior, where the viewsheds all assumed the customer's antenna at 20 feet above ground.)

• On the profiles, the customer is at the left and the tower at the right

• Every tower has a maximum range associated with it, which determines whether it appears In Range or Out of Range. But every tower is included in the computation, regardless of its maximum range. (Well, not quite: under the Settings tab you can set an absolute maximum range for a tower to be included in the computation. It defaults to thirty miles.) With a clear line of sight, you may be able to establish a link beyond a tower's recommended maximum range, but, depending on the equipment you use, connecting beyond the maximum range might have negative effects on other users of the access point.

• The red tint on the profiles indicates area beyond the range given for the tower.

• The <-- and --> under "customer location" let you move back and forth through the spots you've clicked on

• The Streetview button opens a window with Google's Streetview set to the customer location. If the button is bold then that other window will open to an actual Streetview photo; if not, that location hasn't been photographed and you'll get a map

• The get from server and send buttons are a hack for passing locations among staff members. In the demo, the communication is just simulated; it doesn't transmit locations between machines.

• You may be able to integrate with your administrative system by using these URL parameters:

      http://wisp.heywhatsthat.com/?lat=44.3&lon=-69.1
          sets customer location to that lat/lon

      http://wisp.heywhatsthat.com/?address=100+main+st+04843
          looks up the address

  You can add '&elev=999' to set the customer's antenna elevation to 999 meters rather than the default you've set

  We can help with integration issues on a time & materials basis.

• WISP hasn't been tested on many browsers; works fine on Chrome and Firefox 3.5

Questions From Users

• There have been several requests for 400MHz coverage. Because line of sight is the same for any frequency (under our current assumptions, which don't take refraction into account), you can use the system set for 900MHz, but note that
  • The Fresnel zones should be wider at 400 MHz than at 900MHz
  • Towers marked ++ and +++ are within LOS, but +++ may not be 80% free of obstruction
  • We're only computing line of sight, and as frequency drops other factors (e.g. diffraction) become important

• Can we use this in customer facing applications?

  Take a look at our demo customer portal and let us know what you think.

  Also, if you have a customer-facing site where you get their location, we can provide an API for you to get the visibility of all your towers, \and we can help you generate coverage maps.

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  5/2023