Story of missing hiker in Joshua Tree NP

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Re: Story of missing hiker in Joshua Tree NP

Postby OtherHand » Sun Aug 12, 2018 9:38 am

zippetydude wrote:I have no speculation but I do have a couple questions.

You don't think the radius of his possible wandering would expand if he had 2 or 3 times the amount of water?

Didn't the original searching use some approximation of a Bayesian search?

With the huge rock jumbles, almost no amount of searching even just one of these structures would ensure discovery even if he were in there. How could searchers deal with this seemingly intractable problem?


I think if his water supply was much greater than estimated, he would have wandered until he hit civilization or a paved/dirt road and followed it to safety. Unless some accident befell him early on, then the amount of water becomes less relevant. I'm inclined to think he did get into some sort of trouble, which is why I haven't been too focused on the amount of water he was carrying beyond it seeming rather meager. But people do that sort of stuff all the time. Never ME, of course....

All SAR searches are instinctually Bayesian in a sense. The incident manager, based upon experience with earlier searches, assigns teams where it's thought the subject has the highest probability of being. Then as clues or new data come to light, the search areas may change. In the Ewasko search this can be seen just after the incident command received the cell ping data. The next day there were search teams heading into Smith Water despite it being way beyond Ewasko's assumed target (Quail Mtn) and an unlikely place for him to be. But none of this was formal analytics, but rather the judgement of those running the search.

To clear the rock piles you'd almost have to do a series of line searches where searchers move across an area of terrain spread out in a line and keeping a fixed distance between them. Line searches aren't especially efficient and are often used as a last resort in difficult terrain. They are also used in criminal cases when looking for evidence items.
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Re: Story of missing hiker in Joshua Tree NP

Postby Ed » Sun Aug 12, 2018 9:52 am

OtherHand wrote:All SAR searches are instinctually Bayesian in a sense.

Certainly. While the quantitative application of Bayesian statistics can be mathematically complicated, the fundamental principle is that you are simply integrating different sources of information, e.g., old and newer, more subjective and more objective, etc. We all do it informally.
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Re: Story of missing hiker in Joshua Tree NP

Postby Nostromo » Sun Aug 12, 2018 10:19 am

Thanks for the info Tom. I have just seen so much speculation being partly or wholly based on the "fact" of his low water supplies I thought I must have missed it somewhere being definitely stated.

I agree that given his plans to be out of the park early evening and with the ping (relatively) nailing down his location in time and space, it limits the possible scenarios. However, given the amount of time people have spent getting into his head and trying to gauge his decisions, I think his water supply is somewhat more important. At the very least, setting out from the trailhead in extreme heat with 24 oz of water versus 3 or 4 L speaks to two things: planning a much longer hike (both distance and duration) or a much better state of preparedness. Either one of those things could influence the events of his disappearance - not the "where" he ended up so much as the "how". Personally, I think heading out with a couple small bottles of water in the summer heat to hike up Quail or somewhere farther suggests certain mental attitudes: lacking preparedness either through forgetfulness or inexperience (although Bill was said to be experienced in JTNP and Vietnam), having an overactive ego (thinking at 65 he could still do a long range recon style hike with little water like he might have in Vietnam), or perhaps not having a plan to come back at all. Again, all of which could have played a part in the circumstances of "how" he ended up wherever he did.

I mean no disrespect to Bill, which is why I always thought the assumption of his low water supply and his implied attitude or experience somewhat odd. I'd like to give him the benefit of the doubt and say he had much more water, which makes the distance he seemed to have covered in those several days seem less immediately improbable.

EDIT: I just saw your post saying that if he had more water (and was uninjured) he should have been able to find civilization sooner. Have you considered the possibility of mental incapacitation rather than physical? For instance, a moment of exertion causing a brain aneurysm or mild stroke so that he had the water to keep walking (especially resting during the day) but not an idea of where or even who he was. Or possibly, given his Vietnam experience and the SERE training he almost certainly received, actively avoiding civilization or even rescuers if he saw them, believing them to be hostile. If he got better, he found himself in an unfamiliar part of the park with no idea of how he got there. If he got worse, he became physically immobile and crawled somewhere very hidden to wait it out or expire. and I certainly don't have the knowledge to say how long this confusion might have lasted or whether it would have naturally gotten better or worse within a certain timeframe, but it does present a much different way of looking at the evidence than a simple leg injury and dehydration.
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Re: Story of missing hiker in Joshua Tree NP

Postby RichardK » Sun Aug 12, 2018 3:09 pm

Nostromo wrote:Have you considered the possibility of mental incapacitation rather than physical?

That is my theory which I have offered somewhere in the last 70 pages of this thread. There are a variety of ways that Bill could have become non-compos mentis.

- dehydration
- hyperthermia
- a stroke
- a fall hitting his head causing a concussion
- some medical condition like hypertension

Bill wandered in a mental fog. His phone was turned on, but in a cell reception shadow. Sunday morning he walked through a small finger of reception. Note that the cell phone contact was a single ping. He kept on going until he expired in some remote, rough, never visited area. He could well have ended up outside of any of the heavily searched areas.

All of this is raw speculation. However, there have been a bunch of theories offered that go something like this: Bill was too physically injured to return to his car. But, he managed to hobble, drag himself or crawl to this place or that place or some place. I don't believe any of those. If Bill could move, he was going back to his car. Any hiker who runs into trouble will have an overwhelming desire to return to the trailhead.

If speculation could find Bill, he would have been found 5 years ago.
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Re: Story of missing hiker in Joshua Tree NP

Postby Nostromo » Sun Aug 12, 2018 5:28 pm

Well, that was somewhat my point. Thus far, the areas that have been most heavily searched (Smith Water being the prime example) have been so because they were near or on the ping radius, the assumption being that he was immobile and near death when the ping was sent. If you accept the possibility that he kept moving after his phone pinged (possibly for miles) because he was not immobile, your search area suddenly widens again.

You're right, though, that none of this is really helpful. I think, and believe Tom has said as much, that the ping radius was searched and relied on so heavily because it is the only piece of evidence that locates Bill in time and space after he went missing. Otherwise you might as well throw a dart at the map. Unfortunately, I'm starting to think that finding Bill will rely on a random person being in the right place with an extraordinary dose of luck, not any of the speculation that continues to develop. Even if that happens, someone could very well have stepped on a piece of Bill's gear and thought it was nothing more than another careless hiker dropping trash on the trail.
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Re: Story of missing hiker in Joshua Tree NP

Postby Perry » Sun Aug 12, 2018 6:42 pm

Nostromo wrote:Otherwise you might as well throw a dart at the map.

I don't think anybody has tried that method yet. You might be on to something.

But if we're using a Bayesian method, I think the algorithm has to apply a continuously-changing weight on the distance from a searcher's track and also adjust for how rocky the terrain is and whether the terrain is above or below the searcher. Messy yes, but realistic.
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Re: Story of missing hiker in Joshua Tree NP

Postby Nostromo » Sun Aug 12, 2018 10:00 pm

Perry wrote:
But if we're using a Bayesian method, I think the algorithm has to apply a continuously-changing weight on the distance from a searcher's track and also adjust for how rocky the terrain is and whether the terrain is above or below the searcher. Messy yes, but realistic.

Distance from search track yes, terrain type no. At least according to Tom's post on his website, the "simplified Ewasko model" only had three factors: distance from tower, cell coverage, and search tracks (100 feet wide). And if I understand correctly, any piece of the pie within 50 feet of the center of a search track was assigned 0% probability as in Bill was definitely not there, no way we missed him, which may or may not jive with reality. In some types of terrain and vegetation, you might have to pass within 10 feet of some piece of evidence and others you might be able to easily scan 100 feet or more to either side and not miss a thing. But in fairness a simpler robust model is preferable to one with a lot of factors that amount to best guesses.

Remember we're talking 300,000 "cells" here. Unless you come up with a reliable and automated way to assign a value (one that isn't just a wild guess) for each factor with the accessible data, there's no way to do it by hand unless you want a full time job for the next couple years.

Terrain steepness would be easy to do since that information is in the GPS data already, although I'm not sure how much it would help you since that doesn't seem to be as important in search reliability as vegetation cover, for example. Though you could argue steep terrain has a searcher spending more time looking where to place a foot then walking on level ground.

If you had the time, budget, and access to good data you could use satellite imagery and computer vision to automatically adjust the search track factor based on rockiness and vegetative cover. To get good results, you'd need to teach a neural network how to reliably distinguish rocky terrain from thick vegetation from sparse terrain. This:
rocky.JPG (78.46 KiB) Viewed 7216 times
looks very different than this:
shrubs.JPG (65.41 KiB) Viewed 7216 times
to us humans and with enough learning a computer would be able to see the difference too. Then you could adjust the search track factor based on the type of terrain the search went though. Sparse vegetation - the probability within the track is probably effectively zero. If it's a boulder hellscape - the probability would drop off much less quickly with distance from the track. If you had access to historical imagery you could even adjust the vegetation factor based on the specific year and season in which the search took place. Like that heavy wildflower season Tom mentioned during one of his trips made searching much tougher than a drier year with thinner vegetation. Of course, satellite imagery is very different from the reality on the ground so you'd need someone very experienced in this search to cross check the AI and make sure the factor adjustments make some sense.

But who am I kidding. What we really need is one of those silicon valley billionaire types to take an interest and pay a team of code monkeys to hash this out for us. Anybody have an in with Elon Musk?
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Re: Story of missing hiker in Joshua Tree NP

Postby Alchad » Tue Aug 21, 2018 7:13 am


Sorry for this question, being very brief, I've only just come across the "Bill Ewesko" case, but I've been doing a lot of reading, mainly the work done by Tom Mahood, Adam Marsland and the posts on this Forum (but not all!) One thing that puzzles me is regarding his late arrival at the car park, which was supposedly some time after 10.40 in the morning and the fact that the late arrival is thought to be puzzling.

The one seemingly obvious explanation is that he first drives to the Lost Horse Mine Trailhead, ticks off the mine (which apparently was on his list) and then drives back to the Juniper Flats Car Park to start on the Quail Mountain hike.

The timings seem to work, the hike is supposedly only a couple of hours. He was on the road quite early (may have even got into the park before 8 and therefore not registered on the system?).

AS I said, seems obvious, but the missing time has been commented as being a bit of a mystery, when this detour to the Lost Horse Mine would explain it. I know it doesn't really add much to the case itself - except perhaps in that the hike would have taken something out of him, fit 65 year old or not, and influenced his subsequent decisions etc.

Once again, sorry if this has already been covered


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Re: Story of missing hiker in Joshua Tree NP

Postby Osmanthus » Wed Aug 22, 2018 12:50 pm

adamghost wrote:Weeellll....I'm sure you're aware that writers often use a certain flair to make the writing more interesting. So Sherlock Holmes might just be such a device, not to be taken quite this seriously. But as to the logical reasoning I'm quite serious...

So just to engage you here, because you raise some good points, but seem to misunderstand a few things, and it's fun:
I'd be interested to hear your theory.

Here's my delayed response (I forgot about all this, to be honest!), to your reply which was made in a rather better spirit than I made my criticism. My apologies!

I did indeed read most of your blog although I confess that it's very hard not to jump over paragraphs because I think your style could do with being more concise. At the end of the day, that's my problem, not yours. It's your blog after all. I do apologize! I've gone over it again - word by word this time - and my opinion on your use of Sherlock's maxim stands, and your application of Occam's razor. I'll try to re-make my point following the flow of your blog. Apologies to everyone else for the length of this post!

1) Sifting facts section - I'm on-board here, except for this:
>Crucially, this kind of apples-to-apples comparison also tell us that it isn’t enough to just poke holes in someone else’s theory; one has to assert an alternative theory that fits the facts better, using the same criteria, to supplant it.
I disagree on this point. Why should an alternative theory be supplied? A theory is formed when a hypothesis is supported by evidence. If one can find evidence that is inconsistent with the hypothesis - that is, poke holes in the hypothesis - then the theory is weakened accordingly. The theory need not be supplanted by another one; it is enough that the theory is shown to be inconsistent with the facts. As long as we're talking scientific method, this is it. Sure, we don't get anywhere without eventually advancing a better theory, but a faulty theory shouldn't be defended by "you don't have a good theory either!"

2) Skeptic's bias section:
>Occam’s Razor doesn’t mean the simplest answer is almost always right – it just states the simplest hypothesis with the fewest assumptions (very key difference there) should be tested first.
Very true. Occam's razor is a good guide to practical investigation, though it isn't a philosophical truth. On your phrasing, I think an interesting question is: is Occam's razor determined by only the number of assumptions, or also on their quality? If I make one out-there assumption to explain an event, and you make two mundane assumptions, which of our approaches is better applied to Occam's razor?

3) Sherlock Holmes and Deductive reasoning
This is where my first objection came in, and I stand by it: you conflate impossible with improbable.Examples:
>“once you eliminate the impossible, then whatever remains, however improbable, must be the truth.”
> One might break evidence into these categories: definitely true, most likely true, possibly true, most likely not true, giving greater weight to the earlier categories. How do we determine these categories? Again, we use the scientific method – weigh each fact on its own, and weigh the evidence in favor or against its truth, compare them, and see where it takes us.
The second quote is not in line with the first. Sherlock talks in a dichotomy of options; you outline a continuum. To be fair, you do say:
>To knock those things out of consideration we have to show how those things are so unlikely as to be impossible (not just that they sound crazy),
but this is not what you end up practising, in my opinion. You mention three assumptions that you say are awfully unlikely. (By the way, I'm also inclined to believe Mimi Gorman, cautiously, but I don't think there was foul play.) But this is not enough grounds to reject it by Sherlock's maxim. In fact he implies that improbability is certainly not enough to reject a hypothesis. He says "...however improbable, must be the truth". Improbability is not a criterion for rejection, by Sherlock. Maybe it is by Occam's razor! Which you acknowledge. But Sherlock's method is not equivalent to Occam's razor.

Sure, maybe Sherlock is a writer's flair, but in my opinion it is misleading to the reader and logically inconsistent with the rest of your post.

>>("Could Bill have moved his car by himself while a search was underway for him")
>Yup. Talked about that at some length too. I don't know if that could have happened "without realizing" but sure, maybe.

Come now, be fair. You mentioned this in passing but spent much more time on foul play and that inholding. If I'm still missing this then I owe you a beer.

4) Unless something specific happened... [and following]
>The whole U-haul deal was improbable, but when you looked pretty close at the fact pattern, was it really all that more improbable than that Greyson AND Gorman, both park employees, were totally off their hat?

Your caveat following this statement granted, but this is a false dichotomy. The options are not: "Greyson and Gorman are nuts OR the U-Haul!" Other options are self-disappearance, like you say, or a host of other options. Earlier in this thread I suggested that Ewasko lost his phone on the way up in Big Morongo. I'm not married to the theory, but I like it because not only did it not require many assumptions (i.e. Bill loses his phone, realizes it later and goes looking for it), but it also eliminated an assumption (why go north of Quail?) and had explanatory power (i.e. why Bill was late, might possibly explain moving the car). In truth it does have one more assumption if this last is true: it means someone had to not see him moving it. But that's no bigger an assumption than using a U-Haul.

My point is that one can come up with any number of theories that make very few assumptions. The purpose of an assumption is to ensure a theory is consistent with the facts. It does not actually give us reason to believe the theory. This, I think, sums up my objection to the inholding especially, and the U-Haul as well. The only reason you use the inholding in your argument is because it's there and you posited foul play, not because you have any reason to suspect it was involved in foul play. Do you agree that there is a difference?

>>"If the ranger is correct, must there be foul play? Or is it merely likely that there is foul play?"
>Well, again, let me correct the premise. When I was talking about eliminating foul play I specifically talked about THE INHOLDING. So to me, if you can eliminate a means by which Bill can encounter someone on his hike who does him harm and can get rid of his remains, you can pretty much eliminate foul play. Yes, it could have happened at the parking area, but one would expect there to be some evidence of that there, and there wasn't.

You have eliminated nothing. You have only said that some explanations require more (or more difficult) assumptions than others. This is not elimination: it is only an application of Occam's razor.

>But to grapple with your central premise: it's simply not true that all assumptions are created equal and there's no way to assess them - nor that because we can't technically rule out any improbable scenario we can't rule out anything at all. Some things, such as UFO abductions, are technically possible but I think we can rule them out for the purposes of narrowing things down.

I agree with this. My problem is with how you apply it. I suppose the best way I can articulate it is: I think the space of reasonable assumptions is much, much larger than you appear to think it is. My suggestion about losing a phone is just one path to take in this whole space. So is your inholding and U-Haul theory. Another way to say it is that Occam's razor can be applied in a vast number of ways. We could theorize about it all day. The only reason I have to believe your theory is that it suggests a consistent picture with consistent assumptions.

Finally, do believe me when I say Mimi's testimony has always been much more compelling to me than the ranger's. In my post I was speaking from examples. Clearly I should have articulated this better. And for what it's worth, I think the whole dog thing is super weird too.

So in what I hope is a conciliatory point, I agree with your philosophy (except for the Sherlock thing), I just disagree with your application. I don't mean to be aggressive, I just get a bit "animated"!
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Re: Story of missing hiker in Joshua Tree NP

Postby RichardK » Sat Aug 25, 2018 10:02 am

For what it is worth, we passed through the eastern entrance of Yosemite yesterday. Our senior passes were not scanned coming or going. So, the fact that Bill's pass was not scanned means nothing. The gate ranger sees the passes and waves you through.
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