One rule of sliding has always been the Sliding Radius. Basically, this is the geographic landing zone for the Sliders which is constant from world to world thanks to an internal device of the timer called the geographic spectrum stabilizer. Because it is just a landing zone, this means they could activate the timer and slide from a vortex outside the radius...but they would always land on the next world somewhere within the set radius.
Many believed that this radius would change according to each slide...making the timer the moving center point of the radius. However, this is unfeasible for one very large reason. If the radius followed the timer...then the radius would "walk." Let's say for instance that you land in LA...then it's a 400 mile radius from there. Then you land 200 miles south of LA and suddenly there's only half a chance you'll land in LA again. Then you land to the east in Arizona now that it's in the radius...once there, you only have a one fourth chance of landing back in LA. Then you go east again to land in New Mexico and suddenly there's NO chance you'll land even in California. The point is that if the radius did "walk"...we would not have had five years in the California area. The odds are astronomical that they would keep landing there under that type of system.
Now you ask, how could the timer tell where it was? This goes back to the device that governs the radius function - the geographic spectrum stabilizer. As defined, geographic spectrum literally means a range of values of a quantity or set of related quantities in relation to geography. And obviously, a stabilizer is a device which provides accuracy/stability to function (such as in a flying craft - the stabilizer makes the flight smoother and gives a more accurate flight path).
This goes along with another thought presented in my sliding technology explanations. An interdimensional coordinate must work on the same principle as a coordinate in space travel. A coordinate in space travel is not just an assigned number...it is an equation. This equation takes into account movement of the celestial bodies so that you will stay on course and be able to find the destination no matter when you set course. Dimensional coordinates would work on the same principle except that it would obviously entail much more complicated equations.
Now, with that knowledge...the geographic spectrum is a defined set of coordinates (equation) that is constant on every earth they go to (just as a dimensional coordinate would always return you to the same dimension or a celestial coordinate return you to that planet). The stabilizer portion of the device determines how close they land to that defined coordinate (equation). Quinn's original timer had a precise laser gyro stabilizer that would land them within two miles of the coordinate (the two mile rule only taking effect once the timer was advanced and rerouted to work on the power it had left...thus taking power away from the stabilizer). In "Double Cross", the laser gyro stabilizer was replaced with a whispering gallery stabilizer (which worked off sonic principles). This was not as accurate, and thus could only guarantee a landing within 400 miles of the coordinate (equation) laid out in the geographic spectrum.
It is important to note one exception to the sliding radius: dimensional coordinate insertion. This ability was first mentioned in "Exodus", but actually first seen in season three's "Double Cross." At the end of the episode, Logan tracks the Sliders and lands in LA (a vortex opening just where our Sliders vortex last closed). Logan was supposed to be restrained to a two mile radius in San Francisco at that point, but she landed in LA following them. The reason is that tracking a vortex is the same as coordinate insertion; the timer simply follows the photon trail of a Slider in a vortex to its exit point. That exit point is then interpreted as a coordinate and automatically inserted. So, as you can see...dimensional coordinate insertion overrides even the sliding radius and instead makes the exit point at the place the inserted coordinate defines. More examples of this can be found throughout the entire Rickman chase at the end of season three (where the Sliders always landed just where Rickman had). You can also see a more subtle example of this in times when they just returned to a previously saved coordinate. In all those instances, the Sliders again landed at the same location they had last left that world from: Jensen's lab in "Exodus", "Prophets and Loss", and "Slide By Wire."
To understand why we know the radius is a landing zone only, we must look at "As Time Goes By." This episode opens with a world where our Sliders are being deported to Canada. As Arturo, Wade and Remmy leave at 5 am to be deported, it is mentioned that they will be taking Route 1 all the way up to Canada. By noting the top map, you can see this took them over the bridge and on northward. However, Quinn and co. did not road block the convoy until around 10:15 am. Due to the enormous amount of travel time in there, it is very unlikely that they were still within the two mile radius when they slid out. So, this proves that the radius is a landing zone only. They can in fact use the timer outside of the radius, but they would always land within that two mile range no matter where they had left from.
There is also an interesting phenomenon conerning past slides, but which still falls within the confines of the sliding radius. If a slider has previously been to a world, then the next group to go to that world will arrive at the point that last vortex closed if it is inside the defined radius. This has been proven time and again in the series in episodes such as "Into the Mystic", "Post Traumatic Slide Syndrome" and "Exodus" (where the Sliders land on the street in front Quinn's house where the vortex closed after scooping up Remmy).
The "weak spot" factor does have an important limitation though. The only time the phenomenon applies is when there is no overriding factor present in the slide. The first priority is to the inserted coordinate which governs over anything else. Tracking a wormhole is the same as an inserted coordinate, and thus has the same priority. The second priority is the sliding radius; the vortex will not be attracted to "weak spots" outside of the set radius it is confined to. Only if those two circumstances are absent does the "weak spot" theory apply.
In any case, this sliding radius issue never really came to the forefront until the season three episode "Double Cross." In this episode, Logan St. Clair switched out the geospectrum stabilizer in our Sliders timer. She replaced the efficient laser gyro version with a whispering gallery. The decrease in efficiency and accuracy led to a much larger radius for our Sliders to land in. While the laser gyro kept the Sliders landing within a 2 mile area around San Francisco, the new whispering gallery expanded the sliding radius to a 400 mile area around San Francisco.
While we've heard mention of this sliding radius several times since "Double Cross"...we've never been given a real visual of what this means. Until now...
The San Francisco Two Mile Radius
Above are two maps of the San Francisco area. The first offers the full picture of the radius, while the second offers an up-close look of the area which shows the majority of the landmarks we are familiar with from the show and the areas our Sliders were almost landing in in the first two seasons.
I have based the center point around Marina Blvd. (since all addresses given for Quinn's house are fictional and can't be found). Going by evidence from the show, I believe this is where Quinn's house would be located. This reasoning is based on the view we have in the Pilot episode (especially on Ice World). You will notice that from Quinn's front porch you can see out over the Bay and have a view of the Golden Gate Bridge. From the Marina Blvd area, you could have such a view and at the appropriate angle. In season two and three, we always had a view of Quinn's house as just on a residential street. However, the angle was always one way in those instances. My thought is that on Ice World in the Pilot, we were getting the view of a northward gazing perspective from Quinn's house...into the Bay. For the rest of the series, we were getting the southward gazing perspective...which would have had the Bay at "our" backs. The exception is of course season four's "World Killer"...but the Mallory home in that episode wasn't even on a residential street. More than likely, it was in a different location altogether in that dimension.
In conjunction with this perspective obervation, we know that Quinn went to school at Berkeley (located in Golden Gate Park). In the Pilot, we see Quinn traveling to school when he passes over Pacific Ave with the 1400 addresses on the right. The direction he would be traveling by that information would be south...and since Pacific Ave is near the shoreline of the Bay, there isn't much room north of that he could have come from. Once all this is pieced together, we have Marina Blvd as the general area of Quinn's house...and thus the center point of our season one and two sliding radius.
This brings up one of next points. In reality, Berkeley is not located in Golden Gate Park as portrayed on the series. Berkeley is actually about 8 miles northwest of San Francisco. There is in fact no university or school of any kind inside Golden Gate Park. So this is one of the most glaring differences between Earth Prime and our earth. While the two are very close...there are subtle differences such as this.
To the far right and just inside the radius, you will notice a silver spire that represents the TransAmerica tower. This landmark often popped up, but is probably best remembered as the building that the four Sliders clung too on water world at the beginning of "Prince of Wails." It is also this approximate geographic position which they landed once making it to British world in "Prince of Wails" (just on ground level). If you remember, they left that region to soon after cross the bridge over into Oakland (where they found the Oakland Raiders). Yet another bit that fits reality quite nicely.
Moving down this right hand side of the inside portion of the radius, we come to the intersection of O'Farrell and Powell streets (marked by a small green square - Union Square). This section of town is significant because it is the real life location of the San Francisco Chancellor Hotel (the one which brought suit against Universal and caused the name change to Chandler in season four).
Furthermore in this general area, the episode "Fever" gave the address of the CHC as on Polk Street. This is an actual location in San Francisco located to the right hand side of the radius near the center. The entire episode took place around this general area as it didn't take long for the Sliders to travel from place to place throughout the episode.
Also on the right hand side of the radius near the center, there is Geary Avenue. When the Sliders first went into town in the episode "Gillian of the Spirits", they were two blocks away from Geary (where the nearest pay phone was located). The Sliders first landed on that world on the shoreline of the Bay (at what appeared to be the Presidio National Park portion), walking south they would be at about that approximate area (and they did mention how they had been looking for a payphone and had yet to see one - which is why they asked. This suggests they had been walking for a bit).
To the left hand side of the radius, you will note the Golden Gate Bridge near the top of the map. You will also see the Presidio (which our Sliders sometimes landed in, such as in the episode "As Time Goes By"). Below that is a small section of Golden Gate Park. Golden Gate Park was often landed in by the Sliders...but you will notice it was always around the same area (note the recurring park bench). Once you look at the radius, you can see why. On another note, given the angle with which we saw the Azure Gate Bridge in "Post Traumatic Slide Syndrome", the Museum of Interdimensional History was most likely on this left hand side of the radius as well.
One other landing within the confines of our map above is found in "The Good, The Bad and The Wealthy." At the beginning of the episode, the Sliders find themselves on Wall Street. As you see in the map above, there is a significant portion of Market Street within the bottom right corner of the radius. Given the angle by which they saw the bridge and the section of town this was in, it would most likely be the case that Market Street was given a new, slightly changed name on that world.
Another notable mention. Even though our Sliders never landed inside, Alcatraz is within the two mile radius. On the top map you can see mention of Golden Gate National Recreation Area. This is where Alcatraz is located in the North Bay. In the episode "As Time Goes By", the Sliders did arrive in a prison, but the prison was San Quentin (an institution much further north of San Francisco). One has to remember though, that due to the backwards time nature of that world...they didn't actually arrive in that prison. Due to the backwards nature, that is where they were leaving from. Their arrival point did not come until the end of the episode...that location being The Presidio.
The 400 Mile Radius
Above we have a look at the 400 mile radius which governed our Sliders landings in seasons three, four and five. This change led to most of the Sliders' adventures taking place in Los Angeles for the rest of the series (at least those we saw). Of course, there were still a few excursions into San Francisco as well. These visits occurred in episodes like "Double Cross", "The Guardian", "Slither", and "World Killer." But what about all the exceptions and their place in reality?
One of our first exotic locale stops was not named by a real name. The episode was "Desert Storm" and the place was The Sand Pit - a town fully owned by Diggs the bartender (a familiar face from worlds before). Going by the map prominently shown in the episode, the location of this town was approximately where San Bernardino would be.
Picture supplied by Earth62.Net
Next up on our tour would be the town of Paradise from the episode "Paradise Lost." This is a real place located about 100 miles northeast of San Francisco. The town is nowhere near a coastline, however. It could be the fact that in the "Paradise Lost" dimension, a large section of western California had sunk into the ocean...thus creating a shoreline on the doorstep of Paradise.
Once season four arrived, we found ourselves in Colin Mallory's stomping grounds of El Segundo. This is a small suburb of Los Angeles just a few miles to the west/southwest. While in this area, we also have the town of Van Nuys where the events of "Asylum" took place. This is not a town in our reality, but there is a Van Nuys Boulevard running through the Los Angeles area in a north/south direction.
And what would a sliding experience be without a trip to the happiest place on earth? That's right...the famous Chasm of Middletown is located about 50 miles north/northwest of San Francisco.
Later season four also saw our Sliders in Las Vegas. As you can see, Las Vegas is outside the sliding radius by about 20 miles. But...if you remember the episode, the Sliders didn't land in the town. They landed out in the middle of the wilderness and had to catch a ride on the stagecoach in order to reach civilization. The fact is that the Sliders landed on the edge of the radius and then traveled into town...thus observing the rule. The same applies to an event in "Revelations." The gas station and Bates-like motel our Sliders found themselves at was in Needles, CA. This real life town (which really is out in the middle of nowhere) is found at the tip of Nevada just barely inside the California border. Needles is about 40 miles outside of the radius, but we didn't see our Sliders land in Needles. We saw the Sliders land out in the middle of nowhere where they discovered they had 3 1/2 weeks on that world...then suddenly time elapsed between scenes to the Sliders at the gas station just days before the slide. It is quite feasible that the Sliders either walked or hitchhiked to Needles (the first sign of civilization) during that large portion of elapsed time we didn't get to see.
When season five arrived, we also found our Sliders making their first landing in Fresno (an old hometown of Maggie). Unfortunately, the other towns mentioned in season five don't exist...such as Oakwood in "Map of the Mind" and the company town on Route 27 in "Easy Slider" (there is no Route 27 in CA - though strangely enough there is a town called Kincaid, the name of the oil company in the episode. Kincaid is located about 20 miles northeast of Los Angeles).