<p>Would it be possible to use a video camera in the field, and make video recording concurrent with audio recordings? You could then take note of the locations of birds on different branches/locations whenever there is an audio detection, and then manually measure that distance to the recorder at a later time (or use your lazer range finder at night instead to get the range to the location)? I know this is not perfect and assumes that you know, visually, which bird was vocalizing (and assumes you can see the birds). Another approach could be to use a drone with an altimeter to get the height of a bird location, and then use the Pythagorean theorum to get the distance to your recorder.</p>

CC BY-SA 4.0
2022-07-05T14:36:29.140Z
(Answered assuming only a single microphone made measurements and so acoustic localisation would be unavailable)
Chloe
CC BY-SA 4.0
2022-07-01T13:19:04.327Z
2022-07-01T13:19:04.327Z
Chloe
<p>I think most of the answers so far are suggesting you localize via acoustics, while your question seemed to be hinting at measuring distances without the acoustics. If the idea is to try to evaluate animal source levels it seems to me that having a &quot;real life measurment&quot; that does not require the acoustic data to do so is probably best - this is based on the motto that &quot;if you can measure something do so, if not model and estimate it&quot; (I might have just made up that motto). Depending on the scenario, making an exact record of the position of the animal (e.g. taking a bunch of digital photos of the animal while it is making sounds) and then measuring with a tape measure afterwards the exact distance to the cm to your sensor seems a reasonable (and possible optimal) approach to me.</p>

CC BY-SA 4.0
2022-07-05T11:37:48.837Z
2022-07-05T11:37:48.837Z
Tiago Marques
<p>Acoustic localisation or using a total station is neat, of course, but in many cases (at least for my work) a laser range finder and a good old tape measure for distances below 10 meters will do the trick.
I think the Bosch laser range finders are mainly designed for indoor use. I've never had any problems taking distance measures in broad daylight with a Leica range finder (Leica Rangemaster 800).</p>

CC BY-SA 4.0
2022-07-04T10:56:19.610Z
Awesome point about indoor vs outdoor laser range finders! Do you mind sharing the model or series in an edited version of the answer?
Thejasvi
CC BY-SA 4.0
2022-07-04T10:37:43.757Z
2022-07-05T11:19:37.187Z
2022-07-05T11:19:37.187Z
Henrik Brumm
<p>The best way to do this is localization. It won't be easy though. You will need at least three acoustic sensors placed well apart. Search the acoustical society of America for 'Lombard effect' and a lot of the papers will discuss how they estimated source levels of calling animals.</p>

CC BY-SA 4.0
2022-07-03T19:55:16.167Z
2022-07-03T19:55:16.167Z
K.J. Palmer
<p>You could use a <a href="https://en.wikipedia.org/wiki/Total_station" rel="nofollow noreferrer">Total Station</a> to estimate the xyz coordinates and distance of the bird at hand.</p>
<p>Of course a Total Station is a slightly more financially and logistically involved solution (low-end models start at &gt;= 1000 Eu), and is another piece of bulky equipment to carry around and assumes relatively steady ground for the tripod!</p>

CC BY-SA 4.0
2022-07-03T07:34:58.953Z
2022-07-03T07:34:58.953Z
Thejasvi
<p>I'd like to estimate the distance at which the bird is singing from the point of recording, to then finally get the source level from one microphone.</p>
<p>I've seen studies, and heard from colleagues use visual guesstimates and laser range finders. Guesstimation is good, though errors when the bird is nearby (a distance of 1 m instead of 0.5 m makes a big difference to the estimated source level). The laser range finder I have at least doesn't really work well during the day (it's also not a low-end model...Bosch GLM 50).</p>
<p>What are some of the ways I can estimate distance to the bird accurately (or any other diurnal vocalising animal) during daylight?</p>
<p><em>Post-script</em>: The question was initially ambiguous about the number of microphones in play. It has now been edited to specify that Nmics=1.</p>

CC BY-SA 4.0
2022-07-01T09:52:40.063Z
I think the title of your question doesn't match your question (distance vs source level)
Cam Desjonqu
CC BY-SA 4.0
2022-07-01T12:51:30.400Z
Distance is needed to calculate SL, so I'd argue they do match
Chloe
CC BY-SA 4.0
2022-07-03T07:38:14.677Z
I've added distance to the question just in case the SL-distance connection isn't clear for someone searching in a hurry.
Thejasvi
CC BY-SA 4.0
2022-07-04T14:36:54.720Z
based on variation in answers, it would be helpful to specify whether your recordings were made with 1 device or with an array of time-synced devices
Chloe
CC BY-SA 4.0
2022-07-04T14:48:29.143Z
Done. Added one mic to the question.
Thejasvi
<experiment-design><bird><fieldwork>
Estimating distance accurately in the field for bird call source levels?
# Estimating distance accurately in the field for bird call source levels?

(Asked by: username_0 on 2022-07-01)

I'd like to estimate the distance at which the bird is singing from the point of recording, to then finally get the source level from one microphone.

I've seen studies, and heard from colleagues use visual guesstimates and laser range finders. Guesstimation is good, though errors when the bird is nearby (a distance of 1 m instead of 0.5 m makes a big difference to the estimated source level). The laser range finder I have at least doesn't really work well during the day (it's also not a low-end model...Bosch GLM 50).

What are some of the ways I can estimate distance to the bird accurately (or any other diurnal vocalising animal) during daylight?

*Post-script*: The question was initially ambiguous about the number of microphones in play. It has now been edited to specify that Nmics=1.

**Tags:** experiment-design, bird, fieldwork

> **Comments:**
> **username_1**: I think the title of your question doesn't match your question (distance vs source level)  
> **username_2**: Distance is needed to calculate SL, so I'd argue they do match  
> **username_0**: I've added distance to the question just in case the SL-distance connection isn't clear for someone searching in a hurry.  
> **username_2**: based on variation in answers, it would be helpful to specify whether your recordings were made with 1 device or with an array of time-synced devices  
> **username_0**: Done. Added one mic to the question.  

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## 5 answers

### Answer by username_2 on 2022-07-01. Score: 6

Would it be possible to use a video camera in the field, and make video recording concurrent with audio recordings? You could then take note of the locations of birds on different branches/locations whenever there is an audio detection, and then manually measure that distance to the recorder at a later time (or use your lazer range finder at night instead to get the range to the location)? I know this is not perfect and assumes that you know, visually, which bird was vocalizing (and assumes you can see the birds). Another approach could be to use a drone with an altimeter to get the height of a bird location, and then use the Pythagorean theorum to get the distance to your recorder.

> **Comments:**
> **username_2**: (Answered assuming only a single microphone made measurements and so acoustic localisation would be unavailable)  

---

### Answer by username_3 on 2022-07-05. Score: 3

I think most of the answers so far are suggesting you localize via acoustics, while your question seemed to be hinting at measuring distances without the acoustics. If the idea is to try to evaluate animal source levels it seems to me that having a "real life measurment" that does not require the acoustic data to do so is probably best - this is based on the motto that "if you can measure something do so, if not model and estimate it" (I might have just made up that motto). Depending on the scenario, making an exact record of the position of the animal (e.g. taking a bunch of digital photos of the animal while it is making sounds) and then measuring with a tape measure afterwards the exact distance to the cm to your sensor seems a reasonable (and possible optimal) approach to me.


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### Answer by username_4 on 2022-07-04. Score: 3

Acoustic localisation or using a total station is neat, of course, but in many cases (at least for my work) a laser range finder and a good old tape measure for distances below 10 meters will do the trick.
I think the Bosch laser range finders are mainly designed for indoor use. I've never had any problems taking distance measures in broad daylight with a Leica range finder (Leica Rangemaster 800).

> **Comments:**
> **username_0**: Awesome point about indoor vs outdoor laser range finders! Do you mind sharing the model or series in an edited version of the answer?  

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### Answer by username_5 on 2022-07-03. Score: 2

The best way to do this is localization. It won't be easy though. You will need at least three acoustic sensors placed well apart. Search the acoustical society of America for 'Lombard effect' and a lot of the papers will discuss how they estimated source levels of calling animals.


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### Answer by username_0 on 2022-07-03. Score: 0

You could use a [Total Station](https://en.wikipedia.org/wiki/Total_station) to estimate the xyz coordinates and distance of the bird at hand.

Of course a Total Station is a slightly more financially and logistically involved solution (low-end models start at >= 1000 Eu), and is another piece of bulky equipment to carry around and assumes relatively steady ground for the tripod!


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