efontana, If an existing cell phone does not have a sensor you want, then the only alternatives are to make the best use of what you have available, or not to provide the function at all.
By using the variable signal profiling, it is useful for when a dedicated compass sensor is not available in the cell phone. The variability due to a persons body, phone orientation, obstructions, transponder location relative to cell phone, ... all have to be taken into consideration to make a useful product. One potentially useful scenario might be: Instructions for using compass. "Walk in a straight line in the direction the top of the cell phone is pointing; choose a target to walk toward and hold the cell phone flat like you would any mechanical compass. The cell phone will beep when you arrive at the calibration position." "After hearing the beep, rotate about your position smoothly and slowly (4 seconds, 1 second and 1 beep for each 90 degrees), until you return to face your starting position. The display will automatically display the compass bearing around this position." "If you move more than 15 feet from this position, the compass bearing will be removed from the display until Calibration is done for a new position. This prevents the user from using old data." This would be done every time a person wanted a compass bearing. At this one position, they could rotate back and forth and get compass bearing information. When the GPS sensed any new position, the Compass would replace the compass readout with "Perform Calibration". They would have to repeat calibration every time they wanted a compass bearing unless higher level algorithms are running in the background while the user is walking. Updating lookup table(s) with information to derive similar data from moment to moment. Again, this scenario is only useful if a compass sensor is not available in the cell phone. Which is almost all cell phones made today. But I agree, if a compound MEMS chip (with Mag sensor) were incorporated in cell phones then this sensor fusion option would be unnecessary. James On May 19, 5:33 am, "[EMAIL PROTECTED]" <[EMAIL PROTECTED]> wrote: > Hi James, > > This is helpful. Thank you. It is good to know someone is thinking > about this. After reading the IEEE abstract, a little clarification on > use is always helpful. > > Our applications are eyes free, because the phone should not be > competing for those revenue generating resources. So use will happen > with the phone stored on the person’s body, say, in a shirt pocket, > held to the person's ear, or on their belt. The compass needs to work > no matter how the phone is oriented. The IEEE abstract seemed unclear > on how it would work in a handheld device. It would be great for cars, > though. With the two accelerometers, there is a calibration routine > where a person wears the phone normally and walks in one direction. 10 > ft should be enough to get enough calibration to be useful. It can > recalibrate in the background and alarm or adjust ... > > Sensor Fusion is a new word for me. Differential sensors of finite > resolution have been around for a long time. Consider the roach, or > any bug with antennae. They sample air at distant points allowing the > organism to select a direction. The longer the antennae, the smaller > the gradient the organism can detect with sensors of a fixed > resolution. Long antennae help folks figure out what is going on. > Sampling acceleration at distant points is going to give you better > information on angular velocity and acceleration (how fast you are > spinning) than using a single sensor in the same way. > > Thank you for pointing out that radio field interaction can provide > information... since a human body can influence that, it is probably > good to not rely on that method. Two sensors a fixed distance apart > should require little attention and provide good results across many > devices once it is engineered. > > My job is to show why it is worthwhile to spend that dollar for > pedestrians who don’t read maps. Android has the tools to do that, > even in today’s SDK. > > On May 18, 7:48 am, James <[EMAIL PROTECTED]> wrote: > > > > > A MEMS chip can be a collection of sensors (temperature, accelerometer > > (x,y,z), atmospheric pressure, Hall effect sensor (compass), ...) all > > built into the same chip. In mass production the chip could be > > relatively inexpensive. > > >http://ieeexplore.ieee.org/Xplore/login.jsp?url=/iel5/20/35967/017046.... > > > However, an Android shortcut would be to use the GPS sensor and your > > relative direction of travel to produce a compass bearing over 100 > > feet of uniform travel. For each model of cell phone the antenna > > sensitivity changes as you rotate the cell phone about a point. This > > could potentially be tied in with relative position movement to > > estimate a compass bearing about a point. > > > But as I said, the lookup table would be different for each model of > > cell phone. > > > This type of engineering where you take two sensors with low > > resolution to combine their results to provide greater resolution is > > called "Sensor Fusion". > > > Basically a cell phone antenna signal does NOT have the same signal > > profile when you rotate left versus rotate right. This can be > > capitalized upon to determine the relative bearing of which the > > compass is facing. Coupled with the cell phone GPS the relative > > bearing can be referenced to the true bearing. A lookup table can > > provide a correction factor and thereby produce Magnetic Bearing; vis > > vi Compass. > > > James Dunn > > Table of Contents - Similar Insights related to technology > > applicationshttp://blog.360.yahoo.com/jamesbdunn?p=207 > > > On May 15, 9:23 pm, "[EMAIL PROTECTED]" <[EMAIL PROTECTED]> wrote: > > > > I have no idea how much a cell phone with a compass costs. I don't see > > > why it would be expensive if there were enough of a market to micro > > > machine it like all those tiny mirrors. > Who knows these answers? > > > > Thanks, > > > Ed- Hide quoted text - > > > - Show quoted text -- Hide quoted text - > > - Show quoted text - --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Android Discuss" group. 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