How to Run a Wireless Point-to-Point (PtP) Site Survey on Your Phone
Learn how WISP installers and network technicians run fast wireless Point-to-Point (PtP) site surveys, check Fresnel clearance, and calculate mast height on-site.
Every WISP technician and wireless network installer knows the scenario: a link looks completely clear on an office desktop planner on Monday, but when you climb onto the client’s roof on Tuesday, the real world tells a different story.
Perhaps the mounting pole has to go on the lower gable of the roof, a secondary ridgeline sits two kilometers out, or the client wants to know right now whether a standard 2-meter wall bracket will work—or if they need to pay for a 9-meter guyed mast.
Running an accurate wireless Point-to-Point (PtP) site survey directly from your phone lets you verify link viability on the spot before you drill a single hole or unbox a radio.
Why Visual Line of Sight Isn't Enough for PtP Backhauls
Seeing a distant tower with binoculars—or even spotting its strobe light at night—only confirms Visual Line of Sight (VLOS). High-throughput wireless backhauls require RF Line of Sight, which demands an unobstructed elliptical corridor around the direct path known as the First Fresnel Zone.
As a rule of thumb in wireless engineering, you need at least 60% of the First Fresnel Zone free of obstructions to maintain stable modulation (such as 256-QAM or 1024-QAM) without heavy packet loss or multipath reflections.
Even a bare hilltop that sits below your direct visual line can clip the bottom of the Fresnel ellipse, dropping your real-world throughput in half.
Frequency Matters: 5GHz vs. 24GHz vs. 60GHz PtP Links
When surveying a site, the frequency band you choose drastically changes both your Fresnel clearance requirements and how much mast height you need to clear mid-path terrain.
| Band | Typical Hardware | Fresnel Zone Width | Best Use Case & Field Trade-off |
|---|---|---|---|
| 5 GHz | Ubiquiti airMAX / LTU, MikroTik, Cambium ePMP | Wide (Requires more vertical ground clearance) | Medium-to-long range links (3–25+ km); forgiving in rain, sensitive to mid-path terrain ridges |
| 24 GHz | Ubiquiti airFiber 24 | Narrow (Tighter beam, less ground clearance needed) | High-capacity urban/suburban backhauls (1–12 km); avoids 5GHz noise floor |
| 60 GHz | Ubiquiti Wave, MikroTik Wireless Wire | Razor-thin (Almost optical clearance) | Short-to-medium multi-gigabit links (0.5–5 km); minimal Fresnel bloat, affected by heavy rain |
| 900 MHz | Sub-GHz bridges & Meshtastic/IoT telemetry nodes | Very Wide (Large elliptical radius) | NLOS/near-LOS rural links; penetrates light foliage but easily clips ground hills |
Because a 5GHz Fresnel zone is significantly wider than a 60GHz zone (and comparable to 5.8GHz long-range links), a link over a flat valley or low hill might pass a 60GHz clearance check effortlessly while failing a 5GHz check unless you raise the antennas higher above the roof.
Step-by-Step: Conducting a Mobile PtP Site Survey in the Field
Instead of fighting with desktop web planners on a smartphone browser while standing on a ladder, using a native Android tool like LinkSight streamlines the on-site verification process into four quick steps:
1. Lock In Exact Rooftop Coordinates
Desktop pre-planning often places the pin in the center of a parcel or building address. On a large industrial warehouse or rural farm, moving the mounting location by 40 meters can shift your path directly behind a local rise in elevation. Drop Pin A on your exact mounting spot and Pin B on the remote sector or tower.
2. Select Your Operating Frequency
Set the calculator to match your actual deployment band (e.g., 5.8GHz for standard WISP CPE deployments). This ensures the calculated Fresnel zone radius matches the physics of the radio you are mounting.
3. Inspect the 2D Elevation Profile for "Pinch Points"
Once the terrain profile renders, look for the tightest gap between the terrain line and the lower boundary of the Fresnel zone. By dragging your finger along the interactive 2D elevation chart in LinkSight, you can inspect the exact distance, ground elevation, and remaining clearance at every meter along the path.
4. Simulate Mast and Tower Heights (AGL)
If a mid-path ridge clips your Fresnel zone, you do not have to guess how much pipe to add. Adjust the Antenna Height Above Ground Level (AGL) on either end of the link—for example, testing a 3-meter rooftop tripod versus a 10-meter tower—and watch the clearance update instantly. You can give the client an immediate, data-backed quote on the mounting hardware required before leaving the property.
Common Field Mistakes to Avoid
- Ignoring Earth Curvature on Long Hops: On links exceeding 8–10 km, the bulge of the Earth becomes a real physical obstacle near the midpoint. Always rely on a topographic calculator that factors in Earth curvature rather than eyeballing elevation differences.
- Forgetting Seasonal Foliage & Clutter: SRTM topographic data maps bare-earth terrain elevation. If your interactive elevation profile shows your Fresnel zone skimming just 4 meters above a wooded ridge, deciduous trees leafing out in spring will kill the link. Always add a safety margin above forested hills or urban building zones.
- Testing Only One Mounting Spot: Sometimes walking 15 meters to the opposite corner of a flat roof moves the azimuth just enough to shoot through a saddle between two hills instead of straight over a peak.
Verify Every Link Before You Drill
While manufacturer-specific desktop suites have their place in the office, LinkSight gives WISP installers and network engineers a vendor-neutral, native Android utility built for the roof and the field. Drop your pins, inspect the terrain profile with a tap, and confirm your Fresnel clearance in seconds.