> For the complete documentation index, see [llms.txt](https://3dpaws.comet.ucar.edu/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://3dpaws.comet.ucar.edu/building-3d-paws/adding-additional-instruments/stream-storm-surge-gauge.md).

# Stream/Storm Surge Gauge

<figure><img src="/files/1bICmHkJnsQIXnudMKX3" alt=""><figcaption></figcaption></figure>

### How the Sensor Works

The Stream Gauge and Storm Surge Gauge in the 3D-PAWS system utilizes the MaxBotix MB7363 or MB7364 HRXL-MaxSonar-WRLS ultrasonic sensor to provide reliable, high-resolution water level measurements. These rugged, weather-resistant sensors are designed for outdoor environmental monitoring, featuring millimeter-level resolution, a long detection range (up to 10 meters for MB7363 and 5 meters for MB7364), and robust noise rejection algorithms. Their narrow beam pattern and real-time calibration ensure accurate distance readings even in challenging conditions, making them well suited for monitoring stream heights and storm surges in dynamic weather environments.

Please use the extended horn for the Storm Surge Gauge.

### Instruction Slides for Assembling the Stream Gauge

{% embed url="<https://docs.google.com/presentation/d/1MNQdw-ZgiPDAaeQpxELebeudVM-F4yri/edit?ouid=102244773211795243299&rtpof=true&sd=true&usp=sharing>" %}

### **For a sample frame assembly:**

{% embed url="<https://docs.google.com/presentation/d/1nQdoJoT5c6aCyYo4U0bEMxQ9Z9vi58mC/edit?ouid=102244773211795243299&rtpof=true&sd=true&usp=sharing>" %}

### Ultrasonic Sensor Boom Geometry

These sensors emit a **narrow acoustic beam**; if nearby structures such as the mast or seawall are inside the beam path, they can produce unwanted reflections that reduce measurement quality. This section describes a simple, field-ready way to size the **boom length** (horizontal extension from the mast) so that the sensor’s beam clears nearby edges. At greater heights above the surface, the beam expands outward more, so the sensor needs to be placed farther from structures.

For planning purposes, a conservative **20° full beam angle** is assumed. This helps ensure that the sensor’s cone does not intersect the mast or seawall before reaching the surface.

#### Simple rule for boom length

If the mast is installed **right at the edge** (i.e., the mast centerline is at the wall), then:

> **Every 1 meter of sensor height requires about 0.18 meters of boom extension.**

$$
Boom length (m)≈0.176×h
$$

where **h** is the sensor’s height above the water surface in meters.

#### Recommended boom lengths (mast at the edge)

| Sensor height above water (m) | Minimum boom length (m) | Recommended with margin (m)\* |
| ----------------------------: | ----------------------: | ----------------------------: |
|                             1 |                    0.18 |                          0.25 |
|                             2 |                    0.35 |                          0.45 |
|                             3 |                    0.53 |                          0.60 |
|                             4 |                    0.71 |                          0.80 |
|                             5 |                    0.88 |                          0.95 |
|                             6 |                    1.06 |                          1.15 |
|                             7 |                    1.23 |                          1.35 |
|                             8 |                    1.41 |                          1.55 |
|                             9 |                    1.59 |                          1.75 |
|                            10 |                    1.76 |                          1.95 |

\*The “recommended with margin” column adds \~50–100 mm to allow for mast sway, uneven surfaces, and slight variations in actual beam spread.

#### What if the mast *isn’t* at the edge?

If your mast is **set back from the edge**, you must **add the mast-to-edge distance** to the boom length calculated above:

$$
Boom length=(0.176×h)+dedge
$$

Where:

* **h** = height above the water (m)
* **dedge** = horizontal distance from the mast to the edge (m)


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