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Wilderness hikers: 
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Check the current trail conditions rating  

Big Sur Trailmap Garmin maps

Many trail/camp locations on USGS/USFS/WildernessPress/NationalGeographic/Garmin maps of the Big Sur Ventana & Silver Peak Wilderness Areas are incorrect - these Garmin map versions of the on-line Big Sur Trailmap provides accurate trail and camp locations based on local knowledge (mostly GPS'd), and also locally-known "use trails", water sources, waterfalls, and other features in the Ventana and Silver Peak Wilderness areas and in Big Sur state parks. 

Note:  If you own a smartphone but not a GPS, consider using a smartphone app as an "electronic map" - it may well meet all your needs and requires less learning.  If you later want a more capable "electonic map", you can step up to a GPS.  For information on smartphone apps, see Big Sur Trailmap for Smartphones.

Users of a Garmin outdoor GPS [e.g. GPSMAP, Oregon, eTrex 20/30] can load this version of the Big Sur Trailmap directly into their GPS.  It displays all Big Sur Trailmap features except the "historic" trails and camps, i.e those now overgrown and considered "lost".  (If you want to display those, you must separately upload their GPX data).   The "with topography" version also displays 20ft-interval contour lines and intermittent+perennial streams, whereas the "sans topography" version uses a transparent background so features on another loaded map, such as topography/streams/roads/etc, can also be seen (but be warned: that map may also display trails/roads/etc which do not actually exist!) Screen snapshots below depict the Sykes Camp area, displaying a trail, a use trail, and a camp - note that moving the map pointer over the camp or trail or use trail has caused its abbreviated name to be displayed.   For a depiction of these trails, camps, and other features in a browser, on a quadrangle/terrain/satellite background, see the Big Sur Ventana/SilverPeak Trailmap home page. 










Trailmap Legend (icons and line symbology)


       Maps are updated weekly - updated
       Newer Windows systems want to protect you from malicious files, so may display warnings and/or require additional confirmation before downloading or installing these files (because my site does not have a identifying "certificate", which requires $ and administrative time) - those warnings should be ignored
       Windows systems may complain about an "invalid" image file (because the Garmin-format .IMG extension is the same as used by Windows image files) - those warnings should be ignored

     If you find a problem please let me know since the updating is automatic so I do not individually test these files.
     (FYI the most severe problem I've encountered with a bad map is GPS lockup, producing a frozen display which slowly fades - the bad map must then be deleted or overwritten.)


Two Installation Methods are available:

(1)  GPS installation - Direct installation to your GPS memory via USB transfer from your PC/Mac
Simplest, but requires basic PC/Mac file copy/paste/rename knowledge and only installs to GPS

(2)  Garmin BaseCamp/MapSource Software installation and GPS transfer
Installs to both BaseCamp/MapSource PC software and to the GPS.  This has two sub-options: most Windows users will want to use the "Registry Install" executable file, which provides the usual "click to continue" Windows installation experience to install the PC software and allows easy replacement of an existing Big Sur Trailmap in BaseCamp/MapSource.  Mac users and others who want to avoid registry problems should instead use the "Garmin Map Install" (Gmap).  After BaseCamp/MapSource has been installed, it can be used to transfer the map to the GPS. 
Jan 2017 update:   For Mac users:  while installation to BaseCamp will display the Big Sur Trailmap and allow routing, trying to then transfer it to a GPS using BaseCamp's "Install Maps" now FAILS either by not showing a "Big Sur Trailmap" selection or with a message "There is a problem ..." .  For a Mac user, currently the only way of loading the map to your GPS is using the "Direct Installation" method.   If I find a solution to this problem I will delete this message.  (But I might later make a change which unknowingly fixes this problem - if a Mac user later finds a BaseCamp install to GPS works for them, please let me know!)

Other file download options:
• Line+Icon SIZE
See example images above
• WITH/SANS Topography+Streams 
Besides not including topography+streams data, the "SANS" version is transparent so two maps can be displayed on a GPS at the same time (the other map presumably having its own topography, such as Garmin's "Topo24K" maps) - but beware: any incorrect info on the other map, such as the camp locations in "Topo24K", will also be displayed, which can be confusing!  To avoid such problems, I recommend loading the non-transparent "WITH" version for anyone having a newer GPS which can enable/disable individual maps, even if you have another map loaded - then only Trailmap data will be displayed inside the Trailmap region, with the other map being displayed outside that region.  If the other map has info that you wish to use, such as roads not depicted on the Trailmap, I recommend disabling the non-transparent Trailmap map to allow the other map to be displayed when needed, then re-enabling the Trailmap for hiking.  [FYI a free "CAtopo" California topo map can be downloaded to display contour lines over areas outside the Trailmap region.  While a note on that download page recommends using a newer map, I do NOT concur for the following reasons.  The plethora of additional information the newer map includes is seldom useful and clutters up the small screen, making the contour lines harder to read.  And the newer map displays some rivers and streams as intermittent when in fact they are perennial.  Also, the newer map highlights its "trail" lines, which are often incorrect and then misleading and so more harmful than helpful - while trails in the older file often use the same data so can also be misleading, they are thin dashed lines which are easier to ignore. ] 

Note:  On small-screens, table is horizontally scrollable
Routable Trailmap
WITH topography+streams
(non-transparent background)
SANS topography+streams
(transparent background)
SMALL lines+icons Direct GPS Install

BaseCamp Windows Registry Install
BaseCamp Garmin Map Install
Direct GPS Install

BaseCamp Windows Registry Install
BaseCamp Garmin Map Install
MEDIUM lines+icons Direct GPS Install

BaseCamp Windows Registry Install
BaseCamp Garmin Map Install
Direct GPS Install

BaseCamp Windows Registry Install
BaseCamp Garmin Map Install
LARGE lines+icons Direct GPS Install

BaseCamp Windows Registry Install
BaseCamp Garmin Map Install
Direct GPS Install

BaseCamp Windows Registry Install
BaseCamp Garmin Map Install

Supplementary Overlay - Boundary Lines:  To avoid complexity, the above Big Sur Trailmap Garmin files do not display National Forest, State Park, or Wilderness boundary lines.  If desired, these boundaries can also be displayed by downloading this separate Big Sur NF-SP-Wilderness Boundarys overlay map which is transferred to the GPS using the "Direct GPS Install" method described below.  When "Enabled", this transparent-background map displays National Forest (solid brown line), State Park (solid green line), and Wilderness (yellow line with black borders) boundaries on top of the Trailmap features. 

Supplementary Overlay - Soberanes Wildfire Area:  The area burnt by the Soberanes wildfire can be displayed by downloading this separate Sobranes Wildfire overlay map which is transferred to the GPS using the "Direct GPS Install" method described below.  When "Enabled", this transparent-background map displays the wildfire burn area as a black stipple, so the underlying map can also be viewed. 


Summary of the different installation methods:;
  (1) "Direct GPS Install" (and "Supplementary Overlay") downloaded files are copied to a GPS memory directory
  (2) "BaseCamp Windows Registry Install" downloaded files are executed on a PC
  (3) "BaseCamp Garmin Map Install" downloaded files are copied (after unzipping) to a PC directory

(1:Windows) Instructions for "Direct GPS Install" installation into GPS using a Windows PC:
(uses direct PC-to-GPS data transfer via USB cable)
(These instructions work for the GPSs I own - if you find a different procedure is needed for your unit, send me the details and I will add them here). 
Please follow the instructions carefully and exactly - haste makes waste!  Do not delete any file not named "Big Sur Trailmap" - if you mistakenly delete a needed system file, the GPS not operate (and recovery is difficult)! 

  Download:  Download desired "Direct GPS Install" file

  Connect GPS to PC:  You must put your GPS into "USB Mass Storage" mode, which directly connects the GPS memory/storage to the PC.  First turn your GPS off, then connect a USB cable from your GPS to your PC.  Then
On a newer GPS, such as Oregon, GPSMAP62, and eTrex 20/30:
  The GPS will automatically turn on - wait for a "USB Mass Storage mode" screen to appear (either a PC-cabled-to-GPS or a horizontally-pointing trident, sort of) 
On an older GPS, such as GPSMAP60:
  Turn GPS on, select "Main Menu" -> "Setup" -> "Interface" -> "USB Mass Storage" (a "PC-cabled-to-GPS" screen will appear when USB Mass Storage mode is entered) 

  Display GPS memory directory:  Wait for the PC to recognize that a new device has been attached, which is often indicated by a beep from the PC.  On many PCs, a pop-up will then display an "Autoplay" window - you should then click "Open folder to view files using Windows Explorer" which will open at the (highlighted) GPS device -- its name is GPS model and PC specific, an example being "Garmin Oregon (G:)".  It's subdirectories should be displayed, one of which will be "Garmin" (can be capitalized). If that pop-up does not appear, you must then open your PC's "Windows Explorer" program and find the GPS device that has been installed.  If the device's subdirectories are not displayed, then expand (click on the "+") to reveal the "Garmin" subdirectory.  And if your GPS has a microSD card, that device should also be displayed in Windows Explorer, e.g as "Removeable Disk (H:)", and should also have a "Garmin" subdirectory. 

  Copy downloaded file to GPS:  Use Windows Explorer to copy the Garmin-format Trailmap file you downloaded, "BigSurTrailmapWithTopo.IMG" or "BigSurTrailmapSansTopo.IMG", to a "Garmin" subdirectory on your GPS, either in the GPS memory or on the microSD card memory (if installed). 

  Special step for older GPSs:  this special step is NOT NEEDED for newer GPSs such as GPSMAP 62, Oregon, and eTrex 20/30 - do not do this step unless you know it is necessary!  It is needed for older units, such as the GPSMAP60 and pre-20/30 eTrex, which can only have one active map file (though that one file can contain many different individual maps) which must have the Garmin-determined name "gmapsupp.img" (can be capitalized).  If yours is such a GPS, it may already have an existing "gmapsupp.img" file in its "Garmin" directory, in which case it must be replaced with the BigSurTrailmap file - if you wish to preserve that old map data for use at a later time, you must then EITHER (1) rename it on the GPS (e.g. to old-gmapsupp.img) OR (2) move it to the PC for storage OR (3) do both for safety (recommended!).  If you do not wish to preserve it, then delete it.  Now re-name the "BigSurTrailmapWithTopo.IMG" or "BigSurTrailmapSansTopo.IMG" file just loaded onto the GPS's Garmin directory to "gmapsupp.img", so it will become the active map. 

  Deconnect GPS from PC:  Instead of simply unplugging the GPS from the USB cable, to safely remove the USB-enabled GPS it's best to, on the Windows PC, click on the "Open/Close Devices" icon (often a little USB plug and green circle with check mark inside, which should have appeared when the USB Mass Storage mode was established), then click "Eject USB Mass Storage Device" or "Eject (your device name)" , then after the "Safe to remove hardware" message appears the GPS can be disconnected from the USB cable. 

  Display GPS map:  Re-start the GPS - the Big Sur Trailmap should now display in the Big Sur region.  On newer GPS's, one can choose to enable/disable individual map files, generally via "Main Menu" -> "Setup" -> "Map" -> "Map Information".  The Big Sur Trailmap will be indicated by "BigSurTrailmap" - and on some units, e.g. an Oregon, a second "BigSurTrailmap" map with topography+stream data will be found if you installed the version containing those and each map is "enabled" or "disabled" individually.  For additional information see How To Change Which Map Is Displayed On A Garmin GPS

  Usage notes:  The Big Sur Trailmap only takes 1 MB of storage SANS Topography and 44 MB WITH Topography, so if you have a newer GPS and plan to hike Big Sur again, you can just "disable" it as described in the last step, so it can be simply "enabled" on your next hike.  On an older GPS, which required the "special step" above, if you wish to preserve the Big Sur Trailmap for later use you can follow the above steps to again connect the GPS to the PC in USB Mass Storage mode and use Windows Explorer to go to your GPS's "Garmin" directory and reverse the "special step", i.e. re-name "gmapsupp.img" to "BigSurTrailmapWithTopo.IMG" or "BigSurTrailmapSansTopo.IMG" and then restore the original "gmapsupp.img" - or if you wish to restore your GPS to its original condition, then delete the Big Sur Trailmap from your GPS's "Garmin" directory. 

(1:Mac) Instructions for "Direct GPS Install" installation into GPS using a Mac:
(uses direct Mac-to-GPS data transfer via USB cable)
The above detailed instructions for a PC should also work for a Mac with Mac-specific copying methods replacing the PC-specific ones.  In particular, Einar Vollset reports the following abbreviated procedure worked for his Oregon 600:
Please follow the instructions carefully and exactly - haste makes waste!  Do not delete any files - if you mistakenly delete a needed system file, the GPS not operate (and recovery is difficult)! 

  Download desired "Direct GPS Install" .IMG file

  Connect GPS via USB cable and turn on GPS

  Find GARMIN in the "Devices" Menu in Finder

  Drag the .IMG file into the "Garmin" folder under the GARMIN device - note: do not put it into the "Custom Maps" folder

  Disconnect and restart the GPS - map appears in Big Sur region

(2) Instructions for "Registry Install" installation for Garmin BaseCamp/MapSource Software on a Windows PC:
    [Note: the BaseCamp Windows PC version is found here - the older MapSource program, which is no longer being updated, can be found here]
    This procedure executes a program which installs the Big Sur Trailmap into a Windows PC using the Windows Registry. 

•  Ensure that BaseCamp and MapSource are not running! 

•  Run (execute) the downloaded installation file "BigSurTrailmapWithTopo_install.exe" or "BigSurTrailmapSansTopo_install.exe" (generally by double-clicking on its icon) and follow its popup instructions - IF ASKED what directory the files should be installed to, use C:\Garmin.  This creates a "BigSurTrailmap" background map option in BaseCamp/MapSource (selected via a menu on the toolbar). 

•  Note: you can uninstall the Big Sur Trailmap from BaseCamp/MapSource by using your PC's "Control Panel" -> "Programs and Features" (Windows 7 & Vista) or "Add/Remove Programs" (Windows XP) display - then right-click "Uninstall"

    I am not going to treat BaseCamp/MapSource software use - you can find a brief tutorial at the following link:  How To Load Maps On My Garmin GPS Unit (which includes instructions for a Mac).  But note that if using BaseCamp "Install Maps" to update a previously installed Big Sur Trailmap on your GPS you will likely need to do in two steps, first using "Install Maps" to remove the existing GPS map and then using "Install Maps" to add the updated map. 

    If installing on Windows 7 (8/10?) 64-bit PC with newly installed BaseCamp/MapSource:  [Jan 2015]  Some attempts to install this map into an "unused" (newly installed) BaseCamp/MapSource on a Windows 7 64-bit PC have been initially unsuccessful - the map installation goes normally and "Big Sur Trailmap" is found in the Registry ["Control Panel"->"Programs and Features" (Windows 7 & Vista) or "Add/Remove Programs" (Windows XP)] but does not appear in BaseCamp/MapSource.  The current fix is to first install a map found here (which uses a different installer, producing a "used" BaseCamp/MapSource), then install the Trailmap, then uninstall the first map!  Apparently the problem results from "a minor change in how some keys are handled by the operating system which prevented the maps created with the old installer from appearing in Basecamp/MapSource - this only affects computers running Windows 7 64-bit".  It also does not seems to affect previously installed versions of BaseCamp, since I myself run BaseCamp/MapSource on a Windows 7 64-bit PC but have no difficulty in upgrading (or removing and re-installing) the Trailmap.  Alternatively, you can use the "Garmin Map Install" (Gmap) installation procedure described below.

    Windows 10 users:  Registry-based programs can encounter problems in Windows 10.  If such occurs, downloading and installing the "Gmap" ("Garmin Map Install") may work better for you.  Gmap installation for a Mac is described in the following section, but I have no personal experience with Windows to report.  If you gain some, I would appreciate a report on what worked for you.

(3) Instructions for "Garmin Map Install" (Gmap) installation for Garmin BaseCamp/MapSource Software on a Mac:
    [Note: the latest BaseCamp Mac version is found here, a version for older Macs here, and the Windows PC version here]
    This alternative procedure installs a Garmin-format "Gmap" file into a Mac or Windows PC - it is provided for Mac or other users who are unable, or do not wish, to use the "Registry Installation" described above.  Note that this procedure does not use an installation program and so requires some basic computer skills/knowledge.  Also, it will not work for older BaseCamp or MapSource versions. 

For installation on a Mac:

[Note: these instructions use info supplied by others, as I cannot test Mac usage - if it works or doesn't work for you, please let me know - I'll then remove or amend this message]

•  BaseCamp or the latest MapSource must already be installed - but not running!

•  Double-click on the downloaded "Garmin Map Install", "" (a zip format file) to extract the "BigSurTrailmap...gmap" folder file within it

•  Double-click on the extracted file to run "MapManager" (which should automatically be called if BaseCamp/MapSource is installed). 

•  Follow its instructions to complete installation.  The trailmap will then appear as a background map selection in BaseCamp/MapSource when next started. 

For installation on a Windows PC:

•  BaseCamp or the latest MapSource must already be installed - but not running!

•  If the "Registry Installation" version was previously installed that must first be removed by using the "Control Panel"->"Programs and Features" (Windows 7 & Vista) or "Add/Remove Programs" (Windows XP) display to find "Big Sur Trailmap", then right-clicking "Uninstall"

•  The Garmin map installation folder, which varies for different Windows versions, must be found.  It should have been created by the BaseCamp/MapSource installation process - here is some guidance:
       Windows XPC:\Documents and Settings\All Users\Application Data\Garmin\Maps or C:\Documents and Settings\YourUserName\Application Data\Garmin\Maps
       Windows Vista & 7 & ?8/10?C:\ProgramData\Garmin\Maps

•  The downloaded "Garmin Map Install", "" (a zip format file) must be "unzipped" - sometimes Windows Explorer will automatically display the "BigSurTrailmap...gmap" folder file within the zip file, sometimes you must double-click or right-click on the file icon to obtain the "BigSurTrailmap...gmap" folder file within

•  That "BigSurTrailmap...gmap" folder file should be copied into the Garmin map installation folder.  The trailmap will then appear as a background map selection in BaseCamp/MapSource when next started.  Note that this map will not appear in the "Control Panel"->"Programs and Features" (Windows 7 & Vista) or "Add/Remove Programs" (Windows XP) display and cannot be uninstalled in that fashion (since it does not use the Windows Registry). 

•  Note: you can uninstall the Big Sur Trailmap by simply deleting the installed "BigSurTrailmap....gmap" folder or (on a Mac) running the Garmin MapManager program. 

    I am not going to treat BaseCamp/MapSource software use - you can find a brief tutorial at the following link:  How To Load Maps On My Garmin GPS Unit (which includes instructions for a Mac).  But note that if using BaseCamp "Install Maps" to update a previously installed Big Sur Trailmap on your GPS you will likely need to do in two steps, first using "Install Maps" to remove the existing GPS map and then using "Install Maps" to add the updated map. 

Garmin-format Trailmap Usage:

Trail conditions:  Remember that the Ventana/SilverPeak Wilderness Areas are in fact wilderness - trail conditions are highly variable and water sources can be seasonal.  A trail line displayed on the GPS may currently not be passable or followable! You should obtain current information before heading out!  The latest trail condition reports and water information are available on the interactive Wilderness Trail Conditions Map or in the VWA Trail Reports forum

Lines:  Five different trail/road lines are displayed: trails (green+white), use trails (orange+black), dirt gated (red+white) and ungated (red) roads, and paved roads (gray).  Trail and road lines are non-solid so they cannot be confused with user tracks on the GPS, using colors similar to those on the on-line Big Sur Trailmap.  The trail/road name is displayed when the map pointer is over it. 

Icons:  POI (Point of Interest) icons identical to the on-line Big Sur Trailmap (Legend).  icons mark stream crossings on trails which cross the same stream multiple times (e.g., the Carmel River Trail crosses the Carmel River 27 times), since knowing whether the next crossing is near can be useful.  But the icon must be small since if larger would show only a single icon at close-together crossings, negating their usefulness.  The icon name is displayed when the map pointer is over it. 

Search:  POI names can be found using the Garmin "Find"/"Where To" feature, either alphabetically or by category.  For the latter, they are "Geographic Points" with subcategories "Manmade Places" [camps, use camps, campgrounds] or "Water Features" [water sources, waterfalls] or "Land Features" [summits].  Also, trailheads and roadends are listed under "Geographic Points - Land Features"Warning: if another map is also loaded, such as Garmin's "Topo24K", a search will also find its features, which may have the name of a Trailmap feature but be incorrectly located, even if that map is "disabled"

Zoom Levels:  Not all features are displayed at all zoom levels, and this behavior can be changed by GPS setup options (but does not seem to work exactly the same on different GPSs).  So far as I can tell, the trail/usetrail/road lines are always displayed, but the contour lines only appear at smaller scales.  Different icons also appear only at smaller scales, but different icons can appear/disappear at different zoom levels. 

Labels:  Both the lines and icons have names, which can be displayed by moving the map pointer over the line/icon.  In addition, the trails/usetrails/roads have their name automatically displayed on the map at intervals (though that can be turned off if desired - see below).  To save space I've used abbreviations, which can be a bit cryptic.  Unfortunately, the GPS can change my letter capitalizations, so "VDC" may become "Vdc".

User control:  The levels at which icons appear/disappear and the label text size can be controlled under "Setup" -> "Map" with then further menus depending upon the GPS (e.g. "Advanced Map Setup" on the Oregon and GPSMAP62) which control the "Zoom Levels", "Detail Level", and "Text Size". I'm not really sure how all these work or interact with each other.  I do know that a "trail" and "use trail" are considered "streets", so if their persistent map labels bothers you, you can turn off "street labels" - but that does not affect the "roads", for which the labels remain in place! 

Contour and stream lines [for "With Topo" files]:  Contour lines are displayed at 20-ft elevation intervals.  These utilize the most accurate digital terrain data available, comparable to a 1:24000 quadrangle map, but cannot show small-scale ridges and gullies.  The elevation is displayed when the map pointer is over a contour line.  Blue lines depict streams, with intermittent/perennial streams being thin/thick.  Stream location data is not as accurate as the topographic data (it is based on 1:100000 maps) - if the topography shows a gully but the depicted stream is displaced from that gully then likely the actual stream location is in the gully.

Vehicular roads:  The Big Sur Trailmap is intended for hiking, hence the only roads displayed are those which might be used as connectors between trails or for trailhead access.  For the "sans topography" version, another map loaded onto your GPS can provide additional roads since such will be displayed through the trailmap's transparent background (but it may also display roads/trails/etc which do not actually exist!). 

Trailhead/Roadhead POIs:  To provide a greater variety of destination locations, I've created searchable POIs for each trailhead and road end with names ala "Abbreviated Name N/E", with the N/E tail indicating that this trailhead (roadhead) lies North and East of the other one, which would be "Abbreviated Name S/W".  These trailhead POIs are displayed as a small black pushpin icon on the map when zoomed in at high map resolutions, in addition to the usual on-line Trailmap icons.  To keep them from cluttering the "Geographic Points - Manmade Places" POI category which lists camp POIs, I've created them under "Geographic Points - Land Features"

Routable trails: 
    Trails and roads are routable, meaning that within the map coverage area you can can choose a destination (for example by selecting any point along a trail or by a "Find" or "Go To" of a POI) and then select "Go" to have the shortest along-trail route to that point be calculated and displayed.  Routing works in BaseCamp/MapSource as well as on the GPS itself. 
    But you should be able to find your way in the wilderness without needing a GPS to tell you how to get there!  The primary reason for providing this capability is that the along-trail distance to a destination can then be displayed as you hike along, instead of the straight-line distance produced by direct "Off Trail" routing. 
    For this feature to work your GPS's routing options must be set to "Follow Roads", i.e. not to "Direct" or "Off Trail".  Additionally, because this map is intended for hikers it uses the "Activity" setting in a unique way, requiring some GPS-sophistication to utilize.  Since "use trails" can be of questionable hikeability, some people may not want to attempt using them and would not want a routing containing them.  Therefore "use trails" are not used in any routing using "Automobile"> or "Cycling"> modes, whereas they will be used with the "Pedestrian" mode.  [I've experienced some flakiness with "use trails" sometimes being used in "Automobile" mode, though they shouldn't, so have given "Cycling" mode the equivalent functionality as that seems more reliable - experimentation with your unit may be necessary.]  Note that on some models you can have a default routing mode, e.g. "Pedestrian", but once a route has been selected and displayed the "Find" key can then be used to change to another "Activity"; alternatively, you can have opt to have the unit prompt you for the desired "Activity" each time you create a new route. 
    In any event, should the automatically created start-to-finish routing not be what you want, you can create a custom route using "via" points you explicitly select. 
    Two caveats: (see "Details" below for more info)

       • when hiking, the compass arrow will not always point in the "forward" direction and the "distance to destination" can go up-and-down, being too large when the compass arrow is pointing backward.

       • the Garmin-calculated ETA (Estimated Time of Arrival) is not very useful when hiking non-level trails

Details:  My hiking tests find that for slow hiking speeds and poor GPS reception, as often occurs in Big Sur, the Garmin algorithm can have difficulty determining when a trail point has been passed, leading to egregious along-trail "distance to destination" errors - since it thinks you should go back to a point actually passed, the error is twice the distance to the passed point.  This is particularly apt to occur in a series of switchbacks.  Garmin-produced maps also exhibit this behavior.  The current Garmin-format Trailmap uses a work-around to reduce the errors, generally to below 0.1 mile.  Nevertheless, please note that the compass arrow will not always point in the "forward" direction and the "distance to destination" can go up-and-down, being too large when the compass arrow is pointing backward.  Forcing the GPS to re-calculate the route from the current position will will always give the correct distance for the current location.  To do this, some models provide a "route re-calculation" selection, which when used - alternately, you can "stop navigation" and then "resume navigation" or "find a new destination" and then select the same point. 
    Also, the ETA (Estimated Time of Arrival) is usually not useful since I've found Garmin simply assumes a speed of 3 mph in "Pedestrian" mode, which is unlikely to be correct when hiking/backpacking in the wilderness (and even larger speeds are utilized by the "Cycling" and "Automobile" modes). 
    A final issue is that the GPS-calculated along-trail "distance to destination" is around 3-4% smaller than the values I calculate from the same data, e.g. on the route metrics calculation webpage, apparently due to truncation error - since the trailmap trail lines themselves underestimate the actual distance by around 5-10% (as they do not include every small-scale twist and turn along a trail), if I want a truer along-trail "distance to destination" I mentally add 10% (since it is easy to calculate) to the displayed GPS value, knowing it may be an overestimate.  Caveat ambulator! 
    Using along-trail routing requires some GPS knowledge, so you may find "direct (straight-line) routing" simpler to use and less confusing.  One benefit of that mode is its useable ETA, since it uses the computed rate-of-change in straight-line distance to the destination and hence does depend upon one's actual hiking speed. 

Desktop GPS Software:

MapSource and BaseCamp
are Garmin programs which can interact with a Garmin GPS and display GPX waypoint/track data - they only run on Windows and Mac PCs.  The Big Sur Trailmap can be displayed as a background map after the installation procedure described here

Viking desktop GPS data editor and analyzer
A non-Garmin desktop GPX data viewer which can also interact with your GPS similarly to Garmin's MapSource/BaseCamp - it runs on both Windows and Linux PCs.  To use the Big Sur Trailmap tiles as a background map, you must (after installing the Viking program!) install map setup file maps.xml - the exact location depends upon where your system installs Viking, but typically should be in directory "C:\Documents and Settings\username\.viking\" for Windows installations and "/home/username/.viking/" for Linux installations.  To display the Big Sur Trailmap as a background map, under "Layer", "New Map Layer", select "Big Sur Trailmap" (usually the bottom item in the map list) and use its default options, which should have the "Autodownload maps" box checked.  I have tested version 1.4 and 1.6 in Linux, not in Windows.  (Note: Viking uses the Big Sur Trailmap tiles described further at , not the Garmin-format map files described above, so does not have the routing capability of MapSource/BaseCamp). 

If you can provide corrections or additions to this webpage, or if you have an opinion regarding this Garmin-format version and how it might be improved, post to the Trailmap forum.