# Garmin Edge 205 help



## threesixeight (Dec 6, 2005)

I am in need of some advice. I have been reading reviews and post about the Edge 205 and 305. I would like to know some first hand real world experience with the Edge 205 from any of you that has one/used one. Is it accurate mileage wise without the rear wheel mounted sensor that comes with the 305?
I am attracted to the Edge 205 for the main reason that I want to swap this out on 4 different bikes. It is my understanding that all I need to do is have a computer mount on each bike and this can be swapped nothing else to do? I didn't like the ides of using a rear wheel sensor because I would have to buy one for each bike.


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## ScottW (Jan 16, 2004)

I have a 205 and my wife has a 305. You don't have to use a rear wheel sensor for the 305, it is used with the cadence function and as a backup for the GPS based speed/distance function. I find my 205 and her 305 measure consistently. If you don't want the heart rate or cadence function then get the 205 as that is the main difference. Both come with 2 bike mounts so you would need 2 more mounts. I bought mine off the classifieds on MTBR from Geoman. His price was the best I found and shipping was fast.

The accurancy is all based on GPS signal but I have found these to be much much better than older GPS's. I have done rides in Idaho that were heavily wooded and in a canyon and never lost signal. My older hand held Garmin E-trex loses signal in much better conditions. I'm very happy with the Edge.

Once you get it make sure you go to the Garmin website to download the latest software.


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## Hammerli (Jul 23, 2006)

I use the Edge 205, and I have found it to be very accurate (compared to a Cateye wired), and I love the ability to use it running, hiking and biking. I previously owned a Garmin GPSMAP 60CS, and the Edge has far superior accuracy and signal capturing capabilities. I can go into my basement and still get reception, while my GPSMAP 60CS was not able to do that. I'm still trying different software to find one I'm happy with, but as far as the device goes I highly recommend it.


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## Psycho Mike (Apr 2, 2006)

Yeah, the SiRF receivers are great (Edge series, 60 and 70 series) as compared to the older receivers. I was up in Fort Chipewyan, Alberta, Canada and comparing a 70CSX and an older e-Trex Legend. The jackpines are so thinck up there that you can lose sight of a D4 Cat at 30 ft. The Legend was lucky to be +/- 100 ft, the 70 was sitting at +/- 10ft.

Just my observation.


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## threesixeight (Dec 6, 2005)

The 205 is probably all that I need. I didn't realize that you could or would need to download software. I assume it comes with all cords to hook up to a computer. I will search for the best price on a 205.


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## slocaus (Jul 21, 2005)

threesixeight said:


> The 205 is probably all that I need. I didn't realize that you could or would need to download software. I assume it comes with all cords to hook up to a computer. I will search for the best price on a 205.


It will certainly be from GeoMan http://www.geomangps.com/
You might need to ask if he carries it, I'm sure he does; or get the 305 from him for the price of a 205 elsewhere?


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## Speedub.Nate (Dec 31, 2003)

ScottW said:


> I have a 205 and my wife has a 305.


Scott, just the guy I'm looking for!

I'm very curious about the elevation recording differences between the 205 & 305. I am hoping you have a pair of identical rides saved from each unit where you can share the elevation plots with me. I am also curious how well the elevation totals match up between the two units.

Thanks in advance if you are able to share this info.


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## swoodbrn (Oct 5, 2005)

I have the 305. It uses barometric pressure for elevation, whereas the 205 uses only GPS. So, if accuracy of elevation measures is important to you, you'd want to get the 305.


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## Speedub.Nate (Dec 31, 2003)

swoodbrn said:


> I have the 305. It uses barometric pressure for elevation, whereas the 205 uses only GPS. So, if accuracy of elevation measures is important to you, you'd want to get the 305.


Yeah, I'm aware of it... that's why I'm asking. Got any side-by-sides you can show off, if Scott can't produce?


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## GEOMAN (May 30, 2006)

slocaus said:


> It will certainly be from GeoMan http://www.geomangps.com/
> You might need to ask if he carries it, I'm sure he does; or get the 305 from him for the price of a 205 elsewhere?


I'm here for you guys and I ride.

Yes, I have the 305 in stock. We've sold around 1,500 Edge 305's now.

Don't sell many 205's, about 500:1 in favor of the 305. Food for thought. Actually, as I think about it, it's less than that because one of the 205's got exchanged for a 305.

Just got in from my morning trail ride, 24 degrees here in Santa Fe. Of course I had the Edge 305 along. I'd hate to be without it anymore. Great tool and fun to boot.

Thanks for the consideration.


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## ScottW (Jan 16, 2004)

Here is an elevation from a ride we did together. The one on the left is the 305, on the right is the 205. Sorry for the small size, the site wouln't allow me to download a bigger file size.


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## slocaus (Jul 21, 2005)

ScottW said:


> Here is an elevation from a ride we did together. The one on the left is the 305, on the right is the 205. Sorry for the small size, the site wouln't allow me to download a bigger file size.


I'm havin' trouble with right and left on your post; looks like over & under to me!? :skep:


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## ScottW (Jan 16, 2004)

Hmmmmmm, must have to do with screen size. The smoother image is from the 305, the one that is more jagged is the 205.


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## Jesterrider (Feb 22, 2004)

Scott,

Great charts - can you tell us what each unit recorded as total altitude accumulated?

I'm not as worried about smooth versus jagged, but more concerned about total info. I downloaded the pictures, but when I tried to make them larger to review detail they just got too blurry. 

Great info and thanks for the post. I am in the process of deciding between a 205 and 305 and altitude is the final factor.


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## Speedub.Nate (Dec 31, 2003)

Jesterrider said:


> Scott,
> 
> Great charts - can you tell us what each unit recorded as total altitude accumulated?


Hear hear! Thanks for posting that, and confirming my suspicions. As Jester requested, I'd love to know what each unit reported for total elevation gain on those rides.


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## ScottW (Jan 16, 2004)

For that ride the Edge 205 showed 2050 total ascent and 2081 total descent, the 305 showed 1477 total ascent and 1521 total descent.

When comparing a few other rides we have done together the 205 seems to show more ascent and descent, ususally by about 500 ft on a 10+ mile ride. I don't know which one is more accurate but the 205 seems to track a lot of the little ups and downs more than the 305 which smooths the profile so I assume that is where the difference comes from.


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## Speedub.Nate (Dec 31, 2003)

ScottW said:


> ...I don't know which one is more accurate but the 205 seems to track a lot of the little ups and downs more than the 305 which smooths the profile...


Unfortunately, as you've discovered, "total gain" is a bit of a compromise, and bike computers with elevation use a bit of smoothing to make the numbers more real.

For instance, if you are riding on a flat trail, and have a 12" log to cross, should you be credited with a 1' elevation gain?

What if you are riding a very fast rolling singletrack, that is mostly flat, but "rolls" within a 10' or 20' band. No real exertion or elevation gain, but in theory you could be credited with many hundreds of feet of gain. Some bike altimeters will filter out changes less than 10 or 20 feet.

So while the GPS-only plot of the 205 looks overly jagged and likely full of errors, and the barometric altimeter-corrected plot of the 305 appears unnaturally smooth, my guess is that the 305 is more accurate in plot and more relevent in terms of gain data.


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## slocaus (Jul 21, 2005)

Speedub.Nate said:


> Unfortunately, as you've discovered, "total gain" is a bit of a compromise, and bike computers with elevation use a bit of smoothing to make the numbers more real.
> 
> For instance, if you are riding on a flat trail, and have a 12" log to cross, should you be credited with a 1' elevation gain?
> 
> ...


I have not read anywhere about this altitude smoothing effect, but my research has been almost exclusively about the Garmin Map60C(S)(x) and the Edge 205/305 models.

Here is what Garmin states about the Map60CSx elevation readings:


> Elevation computer provides current elevation, ascent/descent rate, minimum/ maximum elevation, total ascent and descent, average and maximum ascent and descent rate.


This elevation data is the reason I choose this unit first; paired with TopoFusion, the log analysis is wonderful - but then I am a techno-weenie.  :thumbsup: I have added an Edge 305 as a tracking GPS and I wanted the barometric altimeter again.



> 42.62 mi (13.69 mi uphill, 12.85 mi downhill, 16.05 mi flat)
> 2750 ft total ascent (2695 ft descent) - 5.2 % uphill grade, 8.9 % downhill grade
> 4:14:56 total time (3:39:56 moving, 0:35:00 stopped)
> 0:05:08 pace (11.6 mph average speed, 33.0 mph max speed)
> 12.402 difficulty, 52.861 effort


I have found that a barometric altimeter is far more accurate than a GPS altimeter. Here is a reference, but it can be off by a +/- 15 meters (50 feet). Here is a good technical explanation.

Here is another general link that is from a great site.

If you want to get *RFT * (Really [email protected]#$%&'n Technical) about GPS elevation, knock yerself out!
Piled higher and deeper. :crazy:

No, I will not post a picture of my propeller beenie! :nono:


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## Speedub.Nate (Dec 31, 2003)

slocaus said:


> I have not read anywhere about this altitude smoothing effect...


I wouldn't call it an effect so much as a byproduct of whatever algorithm they use.

Again, taking the flat trail example (this time completely flat), you have to expect that with either a GPS or a barometric altimeter, either will display some flucuation error -- even if it's only a few feet of "flutter".

If the algorithm doesn't take this into account, the computer is going to add another foot of elevation every time the display fluctuates, and you could rack up quite a bit of elevation gain on a paved, completely level trail. And in reality, the momentary fluctuations are in the 10' to 15' range on a gusty day and even more due to normal inaccuracies of GPS reception.


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## slocaus (Jul 21, 2005)

Speedub.Nate said:


> I wouldn't call it an effect so much as a byproduct of whatever algorithm they use.
> 
> Again, taking the flat trail example (this time completely flat), you have to expect that with either a GPS or a barometric altimeter, either will display some flucuation error -- even if it's only a few feet of "flutter".
> 
> If the algorithm doesn't take this into account, the computer is going to add another foot of elevation every time the display fluctuates, and you could rack up quite a bit of elevation gain on a paved, completely level trail. And in reality, the momentary fluctuations are in the 10' to 15' range on a gusty day and even more due to normal inaccuracies of GPS reception.


I just reread your post above and realized that you were talking about *bike computers* smoothing out elevation readings with an algorithm.

GPSs do no do this. If I ride up and down a 10 foot tall "bump" ten times, I will see an accumulated ascent and descent of 100 feet. My *net* elevations is zero, but I did climb 100 feet along the way.

I'd hate to have a GPSr that reported my going zero miles and zero feet climbing after I do a 35 miles, 8000' climb loop that started and ended at the same point, so it assumed with an algoritm that my net distance and elevation was 0 miles and 0 feet.


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## Speedub.Nate (Dec 31, 2003)

slocaus said:


> I just reread your post above and realized that you were talking about *bike computers* smoothing out elevation readings .


Yes. But a GPS faces the same accuracy problems and I can only assume filters the data in a very similar manner (whether processed inside the unit or on a PC or the MotionBased ap).

Additionally, because GPS units plot a finite number of points along a route and then use those points for distance and elevation calculations, there has to be a threshold of some sort.

I would be curious, in your 10' example, to see what various GPS units report back.

Your 35 mile example is tongue in cheek, no? The various computers I've used will ignore a climb until it records 10-20' of elevation gain, and past that point will begin accumulating. Nowhere am I suggesting anything zero out when you return to your origin.


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## Speedub.Nate (Dec 31, 2003)

Here's some more thoughts on elevation gain I wrote in a recent thread, this one with pictures:

http://forums.mtbr.com/showpost.php?p=2096815&postcount=14


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## slocaus (Jul 21, 2005)

Speedub.Nate said:


> Yes. But a GPS faces the same accuracy problems and I can only assume filters the data in a very similar manner (whether processed inside the unit or on a PC or the MotionBased ap).
> 
> Additionally, because GPS units plot a finite number of points along a route and then use those points for distance and elevation calculations, there has to be a threshold of some sort.
> 
> ...


No filtering in a GPS; bike computers may be different - I have never had one with elevation. My guess is they use only barometric pressure, and not a barometric pressure as a correction to the GPS trackpoints. (shrug)

Here is an example of the first 50 track points from a ride; note that trackpoints are logged every 1 to 20 seconds. The total trackpoints were 893 in a 7.39 mile ride. My 60CSx will record 10,000 track points per file, so there is no need to discard or average anything. The whole idea of a GPS tracklog is to record every point accurately. The software programs I use look at every single trackpoint in there mapping and analysis.

Here is a partial track log, columns are:

```
Index      Time                  Altitude       Leg length       Leg time  Leg course   Position
```


```
1	11/22/2006 7:05:06 AM 	215 ft			0 ft	0:00:01	0.2 mph	54° true	N35 16.702 W120 39.537
2	11/22/2006 7:05:07 AM 	215 ft			0 ft	0:00:01	0.2 mph	76° true	N35 16.702 W120 39.537
3	11/22/2006 7:05:08 AM 	213 ft			8 ft	0:00:38	0.1 mph	254° true	N35 16.702 W120 39.536
4	11/22/2006 7:05:46 AM 	212 ft			24 ft	0:00:18	0.9 mph	316° true	N35 16.702 W120 39.538
5	11/22/2006 7:06:04 AM 	212 ft			26 ft	0:00:14	1.3 mph	350° true	N35 16.705 W120 39.541
6	11/22/2006 7:06:18 AM 	212 ft			40 ft	0:00:08	3 mph	290° true	N35 16.709 W120 39.542
7	11/22/2006 7:06:26 AM 	210 ft			130 ft	0:00:10	9 mph	234° true	N35 16.711 W120 39.550
8	11/22/2006 7:06:36 AM 	210 ft			69 ft	0:00:04	12 mph	250° true	N35 16.698 W120 39.571
9	11/22/2006 7:06:40 AM 	212 ft			321 ft	0:00:17	13 mph	236° true	N35 16.694 W120 39.584
10	11/22/2006 7:06:57 AM 	205 ft			381 ft	0:00:20	13 mph	233° true	N35 16.665 W120 39.637
11	11/22/2006 7:07:17 AM 	201 ft			332 ft	0:00:18	13 mph	233° true	N35 16.627 W120 39.699
12	11/22/2006 7:07:35 AM 	198 ft			362 ft	0:00:20	12 mph	233° true	N35 16.594 W120 39.752
13	11/22/2006 7:07:55 AM 	204 ft			452 ft	0:00:23	13 mph	233° true	N35 16.559 W120 39.810
14	11/22/2006 7:08:18 AM 	199 ft			457 ft	0:00:23	14 mph	234° true	N35 16.514 W120 39.883
15	11/22/2006 7:08:41 AM 	190 ft			354 ft	0:00:18	13 mph	233° true	N35 16.470 W120 39.957
16	11/22/2006 7:08:59 AM 	180 ft			230 ft	0:00:09	17 mph	234° true	N35 16.435 W120 40.015
17	11/22/2006 7:09:08 AM 	174 ft			108 ft	0:00:06	12 mph	274° true	N35 16.413 W120 40.052
18	11/22/2006 7:09:14 AM 	171 ft			277 ft	0:00:18	11 mph	326° true	N35 16.414 W120 40.073
19	11/22/2006 7:09:32 AM 	169 ft			267 ft	0:00:17	11 mph	325° true	N35 16.452 W120 40.105
20	11/22/2006 7:09:49 AM 	169 ft			50 ft	0:00:07	5 mph	330° true	N35 16.488 W120 40.136
21	11/22/2006 7:09:56 AM 	169 ft			143 ft	0:00:11	9 mph	345° true	N35 16.495 W120 40.141
22	11/22/2006 7:10:07 AM 	171 ft			58 ft	0:00:06	7 mph	241° true	N35 16.517 W120 40.148
23	11/22/2006 7:10:13 AM 	171 ft			17 ft	0:00:01	12 mph	193° true	N35 16.513 W120 40.158
24	11/22/2006 7:10:14 AM 	171 ft			92 ft	0:00:05	12 mph	193° true	N35 16.510 W120 40.159
25	11/22/2006 7:10:19 AM 	169 ft			74 ft	0:00:04	13 mph	223° true	N35 16.495 W120 40.163
26	11/22/2006 7:10:23 AM 	172 ft			289 ft	0:00:15	13 mph	243° true	N35 16.487 W120 40.173
27	11/22/2006 7:10:38 AM 	169 ft			136 ft	0:00:09	10 mph	277° true	N35 16.465 W120 40.225
28	11/22/2006 7:10:47 AM 	172 ft			132 ft	0:00:13	7 mph	266° true	N35 16.468 W120 40.253
29	11/22/2006 7:11:00 AM 	175 ft			21 ft	0:00:02	7 mph	279° true	N35 16.466 W120 40.279
30	11/22/2006 7:11:02 AM 	175 ft			95 ft	0:00:09	7 mph	264° true	N35 16.467 W120 40.283
31	11/22/2006 7:11:11 AM 	177 ft			14 ft	0:00:01	9 mph	301° true	N35 16.465 W120 40.302
32	11/22/2006 7:11:12 AM 	175 ft			128 ft	0:00:10	9 mph	303° true	N35 16.466 W120 40.304
33	11/22/2006 7:11:22 AM 	177 ft			80 ft	0:00:06	9 mph	277° true	N35 16.478 W120 40.326
34	11/22/2006 7:11:28 AM 	187 ft			42 ft	0:00:05	6 mph	341° true	N35 16.479 W120 40.342
35	11/22/2006 7:11:33 AM 	188 ft			57 ft	0:00:13	3 mph	10° true	N35 16.486 W120 40.345
36	11/22/2006 7:11:46 AM 	191 ft			20 ft	0:00:12	1.2 mph	40° true	N35 16.495 W120 40.343
37	11/22/2006 7:11:58 AM 	193 ft			5 ft	0:00:15	0.2 mph	78° true	N35 16.498 W120 40.340
38	11/22/2006 7:12:13 AM 	191 ft			3 ft	0:00:15	0.1 mph	153° true	N35 16.498 W120 40.339
39	11/22/2006 7:12:28 AM 	190 ft			52 ft	0:00:15	2 mph	4° true	N35 16.497 W120 40.339
40	11/22/2006 7:12:43 AM 	198 ft			74 ft	0:00:11	5 mph	13° true	N35 16.506 W120 40.338
41	11/22/2006 7:12:54 AM 	209 ft			99 ft	0:00:14	5 mph	12° true	N35 16.518 W120 40.335
42	11/22/2006 7:13:08 AM 	218 ft			108 ft	0:00:16	5 mph	7° true	N35 16.534 W120 40.331
43	11/22/2006 7:13:24 AM 	229 ft			55 ft	0:00:08	5 mph	1° true	N35 16.551 W120 40.328
44	11/22/2006 7:13:32 AM 	234 ft			107 ft	0:00:17	4 mph	13° true	N35 16.560 W120 40.328
45	11/22/2006 7:13:49 AM 	245 ft			77 ft	0:00:13	4 mph	7° true	N35 16.577 W120 40.323
46	11/22/2006 7:14:02 AM 	254 ft			82 ft	0:00:15	4 mph	5° true	N35 16.590 W120 40.321
47	11/22/2006 7:14:17 AM 	267 ft			5 ft	0:00:01	4 mph	355° true	N35 16.603 W120 40.320
48	11/22/2006 7:14:18 AM 	267 ft			58 ft	0:00:10	4 mph	355° true	N35 16.604 W120 40.320
49	11/22/2006 7:14:28 AM 	276 ft			78 ft	0:00:13	4 mph	344° true	N35 16.614 W120 40.321
50	11/22/2006 7:14:41 AM 	284 ft			8 ft	0:00:18	0.3 mph	15° true	N35 16.626 W120 40.325
```
Here is TopoFusion data analysis:

```
1.15 mi (0.40 mi uphill, 0.52 mi downhill, 0.23 mi flat)
132 ft total ascent (60 ft descent) - 7.7 %  uphill grade, 45.8 %  downhill grade 
0:09:35 total time (0:08:42 moving, 0:00:53 stopped)
0:07:32 pace (7.9 mph average speed, 17.4 mph max speed)
```
Here is that track in pic one. It looks jagged since I wanted the scale high to show that there is no smoothing. The entire ride profile is smoother, pic 2. You can still see that there is no smoothing of the profile and you can see the point by point connectors.


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## Speedub.Nate (Dec 31, 2003)

That's very interesting data. Thanks for sharing it, and I'll be sure to play with it tonight.

Two points: First (and this is a technicality, but nonetheless relevent), the data IS filtered, as the elevation data is plotted in 1' increments.

Secondly, I'm not suggesting the GPS receiver should do anything other than report the exact points it records.

However, what is the stated accuracy of the elevation reception of your unit?

Point being, there are a number of data points in there that record changes of 1' to 5' gain, then drop right back down. Now, I can't tell you whether that 1' gain is accurate, or if it is normal variation in reception. 

My guess, however, is there are some normal error fluctuations in there. I would be inclined to apply a 5' to 10' threshold to those numbers. In light of the remainder of the route you rode, I wouldn't necessarily be interested in recording a 4' elevation gain over 300' of level trail (which may or may not be erroneous). I'm much more interested in extended climbs I've exerted myself on, to gain a true appreciation of the difficulty of a particular route (or lack thereof).

However, in the grand scheme of things (given the 1200' you topped out at), this shouldn't have a large impact either way (erroneous or not),


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## Destroy (Jan 12, 2004)

swoodbrn said:


> I have the 305. It uses barometric pressure for elevation, whereas the 205 uses only GPS. So, if accuracy of elevation measures is important to you, you'd want to get the 305.


I'd be curious also to see side by side comparisons between the 2 in regards to elevation. Got any charts yet?


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## Speedub.Nate (Dec 31, 2003)

Destroy said:


> I'd be curious also to see side by side comparisons between the 2 in regards to elevation. Got any charts yet?


Oh, where did I see that... where did I see that...

Found it! Here: http://forums.mtbr.com/showthread.php?p=2529297#post2529297


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## Destroy (Jan 12, 2004)

Found an interesting page on altimeter vs gps...

http://timgiles.free.fr/garminalt.htm


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## Speedub.Nate (Dec 31, 2003)

Destroy said:


> Found an interesting page on altimeter vs gps...
> 
> http://timgiles.free.fr/garminalt.htm


Thanks for sharing. Be interesting to have seen a barometer only plot thrown in there, as well (unsure if the GPS error "influences" the baro calibration at all).


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