The short answer is any one you feel comfortable carrying and using.
Mobile phones cameras are fine and over the last few years, almost any phone would produce an image that would look good on a computer monitor.
You could also use a film, compact, tough or DSLR.
Camera ergonomics and being able to effectively control the camera are a much higher priority than anyone mandating that a specific camera needs to be used.
**Camera/Lens field of view in mm.
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If you were competing in the early 90's film cameras would be the only choice, and some cameras would be compact enough to fit in a jacket pocket. Most wouldnt have zoom and have a fixed wide angle lens (28-35mm in 35mm equivalent)
The field of view of a camera is commonly referred to as a unit in mm. I think it was because it described of how some part of the lens was away from the film. Whatever it actually, means, a lens described as an 14mm lens has a very wide field of view. From the left to the right, it can capture over 90 degrees of light.
Common wide angle lesnes are 28-35mm. having a slightly narrower field of view is a 50mm lens which is commonly used for portraits. Lenses around 200mm are useful for capturing sports and 300mm+ lenses would be useful for getting photos of birds or other far away things.
The mm unit of measure is based on the film or sensor size and was the standard when 35mm film was the widely used. Lenses in compact cameras might actually be something like a 5-14mm lens, but due to the smaller sensor size this might have the equivalent field of view to a 70-200mm lens so figures may be used as '35mm equivalent'.
I have a compact camera which has a 28-300mm lens (35mm equivalent) and i would consider it an excellent choice to be able to capture most wide shots and be able to zoom in on wildlife if the opportunity arose.
Megapixels
A megapixel is a unit of measure for how many millions of pixels are able to be recorded when an image is taken. A Full HD monitor (1920x1080 pixels) can display 2,073,600 pixels. a 4K monitor (3840 x 2160) can display 8294400 which is 4 times as many pixels.
Most relatively new cameras can capture over 10 megapixels, it might have been a consideration when digital cameras were still evolving, but unless you want to print posters or have a super fine magazine cover image, then megapixels shouldnt be a big consideration.
Related, if you are printing, you typically want 150-300 dots per inch to have a nice high resolution print. For A4, i would want to get 300dpi and as the print gets bigger towards a poster, i would be comfortable using a lower dpi as people are less likely to look closely at the details.
You might want a tough camera which is able to be taken in water if you are going to complete more adventurous courses or compete in inclement weather.
Interchangeable lens cameras are also something to consider, but i think having to carry an extra lens during an event and changing it on the fly could be more hassle than its worth.
I dont know about your market, and what is available so i will try and ask some more questions and offer suggestions on what i'd consider taking hiking and travelling.
Does it need to go underwater/ withstand severe weather ?
how will you charge it if your hiking, does it need to take AA batteries so you can get power just about anywhere ? some cameras only charge from mains power.
If i was going well off the beaten track for several months, i'd take my AA battery camera. Compared to all the others, this is the only thing it has going for it. It has a 36-360mm lens (in 35mm equivalent) which means it can a little bit of landscape work, and the zoom can go close in to capture some birds. It can take around 10 megapixel shots, which will be good for an A4 sized print, maybe an A3 sized print. its also around 250grams and can easily fit in a jacket pocket.
If i knew i was going to get super wet or wanted to get some underwater shots, there's my Tough camera. it was designed to go underwater. It has a 25-200mm lens (in 35mm equivalent) which goes wider than the AA camera but doesnt zoom in as much. Its also got some smarts and can take 3 shots in 'landscape' mode and stitch them together to make a panorama. (some image quality is lost, so i would also take 3 shots manually for a higher resolution post production stitch) It does give me a 12megapixel image (and capture RAW images which can help a little bit in post production). This one has a proprietary battery, but can be charged up by USB. This one also has optional external lenses that can be used to go a bit wider or zoom in a bit more.
If i wanted something compact and portable, id take my compact camera. It was designed to be a 'jack of all trades' and has a 28-300mm(35mm) lens. It can shoot 12megapixels and RAW. It fits in a jacket pocket too, but doesnt have any weather sealing. I might use it when its slightly raining, but not for long. It also can have external lenses attached, and ive only used it rarely. I would only take it if i knew id be taking photos of birds.
But if i wanted the best quality, id take my micro 4/3rds camera. This one needs separate lenses. If i wanted to pack light, id get the 12-100mm (24-200mm in 35mm equiv). This camera and body combination is weather sealed and if i could only go for one lens on a round the world trip, this is the one id take. If i could pack more, id consider the 7-14mm too, which lets me get shots about 90 degrees apart from the left to right side. This has all the bells and whistles, and i could make some fairly large prints off it, it normally takes around 20megapixel shots, but can take several shots and merge them into one 80megapixel shot if its on a tripod and nothing in the shot is moving.
I deliberately havent put in camera specifics as what i think is good and works well for me mightn't feel the same to you. If you really want, i can mention camera models, but i dont want them to be taken as go by camera 1, when camera A might be more what you want.