Determine your location from relative FM radio signal strengths

In this post, we’ll take a brief measurement of regular old FM radio stations and try to determine where we are. It’s like a GPS but with local FM transmitters instead of satellites. I did this just for fun. I wonder if it could be used for indoor location and stuff? It is nowhere near as accurate as GPS. But whatever.

calibrated_result1Reading FM radio signal power

The first step is to get a reading of all the nearby radio stations. I used gnuradio and a HackRF One software defined radio. A simple flow-chart that takes the FFT and dumps it to a file is all I needed. I had to throttle the I/O or else my computer would freeze. I used 16M sample rate to have as wide a bandwidth as possible.

The gnuradio flow-chart used to gather data
The gnuradio flow-chart used to gather data

The file sink saves the FFT results in 4-byte integers and just has one 1024-length vector after the other. In a few seconds, I had a 50 MB of data. I did all the post-processing in an external Python script.

Continue reading Determine your location from relative FM radio signal strengths

a few hikes in the seattle area

I’ve been on two hikes in the last 8 days or so. Here’s a brief trip report for both, plus one failed attempt.

Silver Creek to Mineral City

This looked like a cool hike with mines to explore and everything. But, the internet was telling me that the road might be washed out. (Read:

http://www.nwhikers.net/forums/viewtopic.php?p=225991

http://www.troyh.us/OurMovetoSeattle/Hikes/Silver%20Creek%20and%20Mineral%20City/index.html, etc.)

But it was worth a try. Maybe the road has been fixed by now. About that:

Yeah, it's not going to be easy to drive over that
Yeah, it's not going to be easy to drive over that

So we drove to a different nearby hike (5 miles or so).

Lake Serene/Bridal Veil Falls Hike

The first 2 miles are a gradual climb on nice trail. That gets you to the Bridal Veil falls, which are very nice. The next two miles are a tough climb. Tough for me at least. All the other people there were carrying babies or small dogs. On the way back down, Rachel and I had enough energy to go the 0.5 miles up to the upper falls, which were worth it.

Rachel at lower bridal veil falls
Rachel at lower bridal falls
Bad pic of lake serene and mt. index
Bad pic of lake serene and mt. index

The lake was really beautiful. I scrambled around on the snow, of course. That was last weekend. This weekend, we did:

Monte Cristo and Poodle Dog Pass

Mostly because I wanted to find another way down to Mineral City, we decided to try the monte cristo hike. This time, Robert came along. Since this hike is supposed to have a boring and bikable first 4 miles, we loaded bikes into and onto  my jeep and headed out to the Mountain Loop highway. We heard from a ranger that the 1st mile was going to involve us carrying our bikes a lot. He was right. We had to cross a log over the river and get over lots of cables holding the logs in place.

cross the logs
cross the logs

Then the road was a little bumpy for a while, with quite a few trees in the road. Good mountain bikers can get through the rocks, but we were walking for a while. Still, having bikes made the trip to monte cristo fairly painless. Going back down was exceptionally fast. Once in Monte Cristo, we had some lunch and checked out the working train turn table, while scanning the mountains for mines.

lunch at monte cristo
lunch at monte cristo
robert on the railway turntable
robert on the railway turntable

We didn’t see any mines, so we hiked up about 2000 ft. to Poodle Dog Pass. It was a nice hike that took probably 2 hours. Up there we saw lots of snow.

Robert, Rachel, and I up on poodle dog pass
Robert, Rachel, and I up on poodle dog pass

Crystal lake had these incredible water falls coming down from snow-melt. It was breathtaking.

Rachel and the waterfalls above crystal lake
Rachel and the waterfalls above crystal lake

On the way down, we got to see what branches look like from the inside of a tree:

this is what branches look like from the inside
this is what branches look like from the inside

We biked out of there and ate dinner at a Thai place on capitol hill. This whole big-city-right-next-to-mountains thing is nice.

sweet seattle stuff #1

What is there to do near Seattle? Well I’ll make a running list, since I have unlimited publishing rights on this, the website of me. I’ve been here for 2 weeks really and haven’t done as much as I should have. I’ve been busy. But I have found at least three really sweet places on the Eastside.

#1: Denny Park. Wow. It was day 1 and I was just walking through my neighborhood when I found this little street. There’s a trailhead there that descends into deep old-growth, fern-covered forest. As I hiked down, it got prettier and prettier. I got to the bottom to find large moss-covered trees hanging over a stream. I walked for about a mile and found myself at Lake Washington. Hadn’t seen a single person until then. Great suburban hike.

#2: Marymoor Park. Huge park near Redmond. The thing that brings me here often is the free rock-climbing structure. I go there on way home from work occasionally to miss the traffic and boulder around. You can lead-climb here too. It’s actually really cool. It’s made of concrete and rock so it actually feels pretty authentic. There are also RC planes flying nearby every day if you’re into that.

#3: St. Edwards State Park. Ok enough with the state parks already. This one has ~12 miles of fun mountain bike trails. I went on them one morning to check it out and had a great time. There are even some jumps and stuff. Good forest views.

#4: Random lookout. This little pad has a sweet view. You can see Rainier if you go to the far left on a clear day. Good view of gas works park too. Enough to inspire me to go check that out, which was also cool.

Restaurants:

Virginia Inn – Ate outside. Slow service, but I wasn’t in a hurry. The food was good. How’s that for a review?

Thai joint by the AMC in Pacific Place – Mmmmm Thai food. Delicious. Good for before a movie.

Hector’s – mmmm. Fun atmosphere. Got big dinner and bottle of wine to hear some really weird story here. Loved it.

What the Pho? – Pho is in. It’s the new sushi. They heat up meat in broth, where it cooks. Get the well done stuff though as the rare is like, really rare. It was good but not quite as good as sushi. It’s pronounced “fuh,” by the way.

I also had more Thai and conveyor belt sushi and some other stuff but nothing really blew my mind as much as these, as described above.